Fiber reinforcement material, products made thereform, and method for making the same

ABSTRACT

The present invention provides a synthetic fiber and methods for its use and formation. The present invention may comprise a fiber component that is a twisted bundle comprised of multiple strands of a nonfibrillating monofilament, the degree of twist being greater than about 0.9 turns/inch (about 0.36 turns/cm). The present invention may further comprise another fiber component, discrete from the twisted fiber component, that is fibrillated.

CROSS-REFERECE TO RELATED APPLICATIONS

This patent application is a continuation-in-part of, and claimspriority from, U.S. patent application Ser. No. 09/790,353, filed Feb.21, 2001 now U.S. Pat. No. 6,753,081, which is incorporated by referenceherein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reinforcement material and, moreparticularly, to a synthetic fiber material for providing bothstructural and crack-controlling reinforcement to building materials.

2. Description of the Background of the Invention

It is well known that the addition of a reinforcement component tobuilding materials such as cementitious materials, brick, asphalt, andthe like improves the structural integrity of the material and reducesthe likelihood of cracking. When incorporated into cementitiousmaterials such as concrete, for example, the reinforcement component isadded to reduce the effect of two main structural deficiencies: 1) lowtensile strength; and 2) low strain at fracture. The tensile strength ofconcrete is relatively low because concrete, when formed, normallycontains numerous micro-cracks. It is the rapid propagation of thesemicro-cracks under applied stress that is responsible for the lowtensile strength of the material. Because of the widespread use andapplicability of concrete, considerable research has been undertaken tolessen the effects of its deficient structural properties.

Typical reinforcement materials that are added to cementitious materialsinclude, for example, various gauges of wire mesh or reinforcementfibers. A variety of reinforcement fiber additives are known in the artthat provide strength characteristics to building materials. Typicalreinforcement fibers include asbestos fibers, glass fibers, steelfibers, mineral fibers, and cellulose fibers. Some reinforcement fibersare better suited for particular applications than others. For example,asbestos fibers are known to provide effective reinforcement but, due toenvironmental and health concerns, are not extensively used. Inaddition, glass fibers and steel fibers are relatively expensive, andhave a tendency to decompose in cementitious materials. Steel fiberstypically decompose at the surface of the fiber reinforced material,whereas glass fibers continuously undergo decomposition as a result ofthe alkaline nature of cement. Also, due to the physical and chemicalcharacteristics of steel fibers, there is some difficulty in uniformlydistributing the steel fiber throughout the mixture. Furthermore, thereare certain physical and operational deficiencies inherent with steelfiber that reduce its effectiveness. Such deficiencies include, forexample, rebound in air-placed concrete applications, and relativelyhigh equipment costs due to equipment wear from contact with the steelfibers.

It is known that concrete has a tendency to shrink after it has beencast due to the evaporation of excess mixing water. Plastic shrinkagecauses the formation of shrinkage cracks shortly after the casting ofthe concrete, that weakens the matrix thereof. Unlike other fibrousmaterials, synthetic fibers are known to reduce such cracking caused byearly plastic shrinkage. For example, a fibrillated fiber formed from apolyolefin film has been successfully used to prevent or reducecracking. The fibers are stretched multiple times and then cut alonglines at least partially transverse to the direction of orientation. Thefibers are thereby fibrillated. When mixed within cementitiousmaterials, in such a manner that they provide deformations to improveanchoring and bonding within the concrete matrix, the cut fibers aredispersed through the mixture, open to form webs nets, and therebyimprove the strength and binding characteristics of the cementitiousmatrix.

Some advances have been made in the area of fiber reinforcement toprovide increased toughness and durability, and reduce cracking in thematrix of building materials, such as concrete. However, the prior artreinforced fibers have a number of disadvantages that weaken or,otherwise, limit their effectiveness. Accordingly, there is a need foran improved reinforcement fiber that imparts improved structuralproperties to the building materials to which they are added. Inparticular, the need exists for a synthetic reinforcement fiber thatwhen added to, for example, cementitious materials, provides a buildingmaterial that exhibits reduced permeability, increased fatigue strength,improved toughness, and reduced plastic shrinkage.

SUMMARY OF THE INVENTION

In one embodiment, the present invention provides a fiber reinforcementmaterial that includes a plurality of polyolefinic strands ofmonofilaments of about 350 to about 6000 denier per filament, twisted toform a fiber bundle, the degree of twist being greater than about 0.9turns/inch (0.36 turns/cm).

In another embodiment, the present invention provides a reinforcementfor cementitious material that includes a plurality of polyolefinmonofilaments, the plurality of monofilaments being in a twistedconfiguration, the degree of twist being greater than about 0.9turns/inch (about 0.36 turns/cm).

The present invention also provides a reinforced cementitious materialthat includes a cementitious mass and a fiber component dispersedthroughout the mass. The fiber component is a plurality of polyolefinicstrands of monofilaments of about 350 to about 6000 denier per filament,twisted to form a fiber bundle, the degree of twist being greater thanabout 0.9 turns/inch (about 0.36 turns/cm).

The present invention also provides a reinforcement material for acemetitious material formed by twisting a plurality of polyolefinicstrands of monofilaments into a fiber bundle for mixing into acementitious mass, the degree of twist being greater than about 0.9turns/inch (about 0.36 turns/cm).

In another embodiment, the present invention provides a synthetic fiberblend for use as reinforcement for cementitious material, which includesa first fiber component and a second fiber component. The first fibercomponent is fibrillated and formed of a homopolymer material. Thesecond synthetic fiber component is a copolymer that is discrete fromthe first fiber component and is a plurality of monofilaments twisted toform a non-interconnected bundle, the degree of twist being greater thanabout 0.9 turns/inch (about 0.36 turns/cm).

In yet another embodiment, the present invention provides a syntheticfiber blend for use as reinforcement for cementitious material thatincludes a first fiber component and a second fiber component. The firstfiber component is formed from a homopolymer of polypropylene and iscomposed of fibers in fibrillated form. The second fiber component,discrete from the first fiber component, is formed from a copolymer ofpolypropylene and high-density polyethylene, and is composed of bundlesof monofilaments that have been twisted, the degree of twist beinggreater than about 0.9 turns/inch (about 0.36 turns/cm).

The present invention also provides a synthetic fiber blend for use asreinforcement for cementitious material that includes a first fibercomponent and a second fiber component. The first fiber component isfibrillated and is formed of a homopolymer polypropylene fiber. Thesecond fiber component is discrete from the first fiber component and isa copolymer formed of a polypropylene and a high density polyethylene.The second fiber component is a plurality of monofilaments twisted toform a non-interconnected bundle, the degree of twist being greater thanabout 0.9 turns/inch (about 0.36 turns/cm).

In another embodiment, the present invention provides a synthetic fiberblend for use as reinforcement for cementitious material that includes afirst fiber component and a second fiber component. The first fibercomponent is fibrillated and formed of a homopolymer polypropylenefiber. The second fiber component is discrete from the first fibercomponent, is a copolymer formed of a major amount of a polypropyleneand a minor amount of a high density polyethylene, and includes aplurality of monofilaments twisted to form a non-interconnected bundle,the degree of twist being greater than about 0.9 turns/inch (about 0.36turns/cm). The first fiber component is present in the synthetic fiberblend in amounts ranging from about 5 to about 50 by total weightpercent, while the second fiber component is present in the syntheticfiber blend in amounts ranging from about 50 to about 95 by total weightpercent.

In another embodiment, the present invention provides a reinforcedcementitious material, comprising a synthetic fiber blend distributedthrough a matrix of the cementitious material, the synthetic fiber blendincluding a first fiber component and a second fiber component. Thefirst fiber component is formed of a homopolymer polypropylene fiber.The second fiber component is discrete from the first fiber component,is a copolymer formed of a polypropylene and a high densitypolyethylene, and includes a plurality of monofilaments twisted to forma non-interconnected bundle, the degree of twist being greater thanabout 0.9 turns/inch (about 0.36 turns/cm).

The present invention also provides a method of forming a reinforcementfor cementitious material. The method includes twisting a plurality ofpolyolefinic strands of monofilaments of about 350 to about 6000 denierper filament into a fiber bundle for mixing into a cementitious mass toform the cementitious material, the twisting occurring to a degree thatis greater than about 0.9 turns/inch (about 0.36 turns/cm).

In another embodiment, the present invention provides a method offorming a reinforced cementitous material. The method includes adding toa cementitious mass a plurality of polyolefinic strands of monofilamentsof about 350 to about 6000 denier per filament twisted to form the fiberbundle, the degree of twist being greater than about 0.9 turns/inch(about 0.36 turns/cm).

The present invention also provides a method of forming a syntheticfiber blend. The method includes blending a first fiber component with asecond fiber component. The first fiber component is fibrillated andformed of a homopolymer polypropylene fiber. The second fiber componentis discrete from the first fiber component, is a copolymer of apolypropylene and a high density polyethylene, and is twisted to form afiber bundle, the degree of twist being greater than about 0.9turns/inch (about 0.36 turns/cm).

In yet another embodiment, the present invention provides a method ofreinforcing a material that includes mixing a synthetic fiber blend witha cementitious material. The synthetic fiber blend includes a firstfiber component and a second fiber component. The first fiber componentis fibrillated and formed of a homopolymer polypropylene fiber. Thesecond fiber component is discrete from the first fiber component, is acopolymer formed of a major amount of polypropylene and a minor amountof high density polyethylene, and is twisted to form a fiber bundle, thedegree of twist being greater than about 0.9 turns/inch (about 0.36turns/cm).

Also provided is a fiber reinforcement material, comprising a pluralityof polyolefinic strands of monofilaments of about 350 to about 6000denier per filament, twisted to form a fiber bundle, the degree of twistbeing greater than about 0.9 turns/inch (about 0.36 turns/cm), whereinthe plurality of strands of monofilaments are twisted to form anon-interconnected bundle in the absence of a wetting agent.

In another embodiment, a fiber reinforcement material is provided,comprising a plurality of polyolefinic strands of monofilaments of about350 to about 6000 denier per filament, twisted to form a fiber bundle,the degree of twist being greater than about 0.9 turns/inch (about 0.36turns/cm), wherein the plurality of strands of monofilaments form afirst fiber component, the fiber reinforcement material furthercomprising a second fiber component that is discrete from the firstfiber component and is fibrillated and formed of a homopolymer material.

In addition, a reinforcement for cementitious material is provided,comprising a plurality of polyolefin monofilaments, the plurality ofmonofilaments being in a twisted configuration, the degree of twistbeing greater than about 0.9 turns/inch (about 0.36 turns/cm), whereinthe plurality of monofilaments are twisted to form a non-interconnectedbundle in the absence of a wetting agent.

In another embodiment, a reinforcement for cementitious material isprovided, comprising a plurality of polyolefin monofilaments, theplurality of monofilaments being in a twisted configuration, the degreeof twist being greater than about 0.9 turns/inch (about 0.36 turns/cm),wherein the plurality of monofilaments form a first fiber component, thereinforcement for cementitious material further comprising a secondfiber component that is discrete from the first fiber component and isfibrillated and formed of a homopolymer material.

Also provided is a reinforced cementitious material, comprising acementitious mass and a fiber component dispersed throughout the mass,the fiber component being a plurality of polyolefinic strands ofmonofilaments of about 350 to about 6000 denier per filament twisted toform a fiber bundle, the degree of twist being greater than about 0.9turns/inch (about 0.36 turns/cm), wherein the plurality of strands ofmonofilaments are twisted to form a non-interconnected bundle in theabsence of a wetting agent.

In another embodiment, a reinforced cementitious material is provided,comprising a cementitious mass and a fiber component dispersedthroughout the mass, the fiber component being a plurality ofpolyolefinic strands of monofilaments of about 350 to about 6000 denierper filament twisted to form a fiber bundle, the degree of twist beinggreater than about 0.9 turns/inch (about 0.36 turns/cm), wherein theplurality of strands of monofilaments form a first fiber component, thereinforced cementitious material further comprising a second fibercomponent that is discrete from the first fiber component and isfibrillated and formed of a homopolymer material.

Also provided is a reinforcement material for a cementitious materialformed by twisting a plurality of polyolefinic strands of monofilamentsinto a fiber bundle for mixing into a cementitious mass, the degree oftwist being greater than about 0.9 turns/inch (about 0.36 turns/cm),wherein the plurality of strands of monofilaments are twisted to form anon-interconnected bundle in the absence of a wetting agent.

In another embodinment, provided is a reinforcement material for acementitious material formed by twisting a plurality of polyolefinicstrands of monofilaments into a fiber bundle for mixing into acementitious mass, the degree of twist being greater than about 0.9turns/inch (about 0.36 turns/cm), wherein the plurality of strands ofmonofilaments form a first fiber component, the reinforcement materialfurther comprising a second fiber component that is discrete from thefirst fiber component and is fibrillated and formed of a homopolymermaterial.

In yet another embodiment, a fiber reinforcement material is provided,comprising a plurality of polyolefinic strands of monofilaments of about350 to about 6000 denier per filament, twisted to form a fiber bundle inthe absence of a wetting agent.

In addition, provided is a reinforcement for cementitious material,comprising a plurality of polyolefin monofilaments of about 350 to about6000 denier per filament, the plurality of monofilaments being in atwisted configuration in the absence of a wetting agent.

Also provided is a reinforced cementitious material, comprising acementitious mass and a fiber component dispersed throughout the mass,the fiber component being a plurality of polyolefinic strands ofmonofilaments of about 350 to about 6000 denier per filament twisted toform a fiber bundle in the absence of a wetting agent.

In another embodiment, provided is a reinforcement material for acementitious material formed by twisting a plurality of polyolefinicstrands of monofilaments of about 350 to about 6000 denier per filamentinto a fiber bundle in the absence of a wetting agent for mixing into acementitious mass.

In yet another embodiment, a reinforced cementitious material isprovided comprising a synthetic fiber blend distributed through a matrixof the cementitious material. The synthetic fiber blend comprises afirst fiber component formed of a homopolymer polypropylene fiber, and asecond fiber component being discrete from the first fiber component andbeing a copolymer formed of a polypropylene and a high densitypolyethylene, the second fiber component being a plurality ofmonofilaments of about 350 to about 6000 denier per filament twisted toform a fiber bundle in the absence of a wetting agent.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and advantages of the present invention may bebetter understood by reference to the accompanying drawings, whereinlike reference numerals designate like elements and in which:

FIG. 1 illustrates a comparison between the crack areas in slabscontaining different amounts of the synthetic fiber blend of the presentinvention based on percent by volume;

FIG. 2 illustrates a comparison between the length to width ratios ofcracks in slabs containing different amounts of the synthetic fiberblend of the present invention based on percent by volume;

FIG. 3 illustrates a comparison between the time of the appearance ofthe first crack in slabs containing different amounts of the syntheticfiber blend of the present invention based on percent by volume;

FIG. 4 illustrates a comparison between crack areas between controlslabs and slabs containing different amounts of the synthetic fiberblend of the present invention based on percent by volume;

FIG. 5 illustrates a comparison between crack area as a percentage ofcontrol in slabs containing different amounts of the synthetic fiberblend of the present invention based on percent by volume;

FIG. 6 illustrates a comparison of crack area reduction in slabscontaining different amounts of the synthetic fiber blend of the presentinvention based on percent by volume;

FIG. 7 illustrates a comparison between the first crack strength inslabs containing different amounts of the synthetic fiber blends of thepresent invention based on percent by volume;

FIG. 8 illustrates a comparison between the modulus of rupture in slabscontaining different amounts of the synthetic fiber blends of thepresent invention based on percent by volume;

FIG. 9 illustrates a comparison between the first crack toughness inslabs containing different amounts of the synthetic fiber blends of thepresent invention based on percent by volume;

FIG. 10 illustrates toughness indices versus fiber content in concreteslabs having different amounts of the synthetic fiber blends of thepresent invention based on percent by volume;

FIG. 11 illustrates Japanese toughness indices versus fiber content inconcrete slabs having different amounts of the synthetic fiber blends ofthe present invention based on percent by volume;

FIG. 12 illustrates Japanese flexural strength versus fiber content inconcrete slabs having different amounts of the synthetic fiber blends ofthe present invention based on percent by volume;

FIG. 13 illustrates average residual strength versus fiber content inconcrete slabs having different amounts of the synthetic fiber blends ofthe present invention based on percent by volume;

FIG. 14 illustrates the number of blows to first crack and failureversus fiber content in concrete slabs having different amounts of thesynthetic fiber blends of the present invention based on percent byvolume;

FIG. 15 illustrates an average stress—deflection diagram comparingflexural stress versus deflection at 1.0% by volume;

FIG. 16 illustrates a stress—deflection diagram comparing flexuralstress versus deflection of the synthetic fiber blends of the presentinvention at 1.0% by volume;

FIG. 17 illustrates a stress—deflection diagram comparing flexuralstress versus deflection of the synthetic fiber blends of the presentinvention at 1.0% by volume;

FIG. 18 illustrates a stress—deflection diagram comparing flexuralstress versus deflection of the synthetic fiber blends of the presentinvention at 1.0% by volume;

FIG. 19 illustrates a stress—deflection diagram comparing flexuralstress versus deflection of the synthetic fiber blends of the presentinvention at 1.5% by volume;

FIG. 20 illustrates a stress—deflection diagram comparing flexuralstress versus deflection of the synthetic fiber blends of the presentinvention at 1.5% by volume;

FIG. 21 illustrates a stress—deflection diagram comparing flexuralstress versus deflection of the synthetic fiber blends of the presentinvention at 1.5% by volume;

FIG. 22 illustrates a stress—deflection diagram comparing flexuralstress versus deflection of the synthetic fiber blends of the presentinvention at 1.5% by volume;

FIG. 23 illustrates a stress—deflection diagram comparing flexuralstress versus deflection of the synthetic fiber blends of the presentinvention at 1.9% by volume;

FIG. 24 illustrates a stress—deflection diagram comparing flexuralstress versus deflection of the synthetic fiber blends of the presentinvention at 1.9% by volume;

FIG. 25 illustrates a stress—deflection diagram comparing flexuralstress versus deflection of the synthetic fiber blends of the presentinvention at 1.9% by volume;

FIG. 26 illustrates a stress—deflection diagram comparing flexuralstress versus deflection of the synthetic fiber blends of the presentinvention at 1.9% by volume;

FIG. 27 illustrates a load deflection plot comparing load versus centraldeflection of the synthetic fiber blends of the present invention in ashotcrete panel at 1.0% by volume;

FIG. 28 illustrates a load deflection plot comparing load versus centraldeflection of the synthetic fiber blends of the present invention in ashotcrete panel at 1.5% by volume;

FIG. 29 illustrates a load deflection plot comparing load versus centraldeflection of the synthetic fiber blends of the present invention in ashotcrete panel at 1.9% by volume;

FIG. 30 illustrates an embodiment of the present invention wherein thesecond fiber component is twisted at a particular degree of twisted,identified as X; and

FIG. 31 illustrates a problem in the prior art, wherein the individualstrands of monofilament have some splitting and “paint brush” effect.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is to be understood that the figures and descriptions of the presentinvention have been simplified to illustrate elements that are relevantfor a clear understanding of the present invention. Those of ordinaryskill in the art will recognize that associated elements and other itemsmay be employed in the implementation of the present invention. However,because many such associated elements and items are well known in theart, they will not be discussed herein.

In the present detailed description of the invention, the invention willbe illustrated in the form of a synthetic fiber reinforcement materialfor incorporation into a cementitious material. It will be understood,however, that the invention is not limited to embodiment in such formand may be used with any building materials and compositions relatingthereto that use fibrous materials to improve structural strength orintegrity. Such materials and compositions include, but are not limitedto, cement, concrete, shotcrete, mortar, grout, asphalt, and the like.Thus, while the present invention is capable of embodiment in manydifferent forms, for ease of description this detailed description andthe accompanying drawings disclose only specific forms as examples ofthe invention. Those having ordinary skill in the relevant art will beable to adapt the invention to application in other forms notspecifically presented herein based upon the present description.

Relative to wire mesh, the synthetic fiber reinforcement materials ofthe present invention provide a more effective and cost efficient meansof reinforcement. This is so because even relatively small amounts offiber, when added to the cementitious mixture, are distributedthroughout the mixture to significantly reinforce the entire matrixmaterial, reduce permeability, increase fatigue strength, and improvetoughness. In addition, application of wire mesh reinforcement isrelatively time and labor intensive due to the placement demandsassociated therewith.

By way of example, the synthetic fibers of the present invention may beincorporated into various cementitious building materials and productsused for building or construction such as, for example, structuralpavements, airport runways and tarmacs, bridge deck overlays andbarriers, structural floor slabs, pre-cast concrete products such aspipes and tanks, tilt-up wall panels, shotcrete for rockfillstabilization, tunnel linings and dome structures. The synthetic fiberblend of the present invention may also be used for repair,rehabilitation, retrofit and renovation of existing products orstructures such as, for example, in overlays, whitetoppings, and repairsof airport pavements and bridge decks. It will be understood, however,that only a limited number of applications are present herein, and thatthe present invention may be used in connection with the construction ofall materials that employ reinforcing fiber material.

In addition to structural reinforcement, the incorporation of thesynthetic fiber blend of the present invention in, for example, castcementitious material modifies the cracking mechanism and reduces thepropagation of micro-cracking caused by concrete shrinkage. Accordingly,relative to non-reinforced cement, the resultant cracks of fiberreinforced concrete of the present invention are smaller in width, thepermeability of the material is reduced, and the ultimate crackingstrain is enhanced. Furthermore, the blended fibers of the presentinvention are capable of carrying a load across the crack. In addition,as will be discussed below, tests of the fiber reinforced concrete ofthe present invention indicate that the concrete material has improvedtoughness or residual load carrying ability after the first crack, andmay have substantially improved impact resistance.

The present invention is directed to a hybrid blend of high performancesynthetic fibers and, more particularly, to a blend of synthetic fibersto reduce the effects of plastic shrinkage and improve hardened concreteproperties. As will be discussed in greater detail below, it has beendiscovered that the combination of a first component fiber and a secondcomponent fiber to form the hybrid fiber blend of the present inventionachieves surprising reinforcement properties and a variety ofperformance benefits greater than that of which each fiber component isindividually capable. In particular, the fiber of the present inventionimproves control of plastic and settlement shrinkage cracking whileimproving impact strength, concrete toughness and other structural andlong-term durability properties.

The first fiber component is a homopolymer polypropylene fibrousreinforcement material. The first fiber component is a collated,fibrillated (network) fiber that may be approximately 100 to about20,000 denier per filament. For example, in one embodiment of thepresent invention the first fiber component is approximately 10,000denier per filament and includes the following physical properties:

PHYSICAL PROPERTIES OF THE FIRST FIBER COMPONENT Material VirginHomopolymer Color Gray Polypropylene Form Collated Fibrillated FiberAcid/Alkali Excellent Resistance Specific 0.91 Absorption Nil GravityTensile 28–40 ksi. (200–272 Mpa) Compliance A.S.T.M. C-1116 StrengthLengths 2¼″ (54 mm)

The first fiber component may, but need not, be formed of 100 percentvirgin polypropylene, and may be a color blended and fully orientedfiber that is substantially non-corrosive, non-magnetic, and alkalineresistant. When used alone as a fiber reinforcement additive (i.e. notas a hybrid blend in combination with the second fiber component,discussed below, as disclosed herein), the first component is typicallyadded at a dosage rate of 1.5 pounds per cubic yard (0.9 kilograms percubic meter) of cementitious material directly to the mixing systemduring, or after, the batching of the other ingredients and mixed at atime and speed recommended by the mixer manufacturer (typically four tofive minutes). The first fiber component exhibits good mixing anduniform distribution properties. The resultant fiber reinforced materialprovides relatively good long term durability and secondary/temperaturecontrol for temperature/shrinkage cracking.

When used in the present invention, the first fiber component may beadded to the hybrid mixture in amounts of about 5 to about 50 by totalweight percent. For example, in one embodiment of the present invention,the first fiber component may be added in amounts of about 6.7 totalweight percent. In addition, the first fiber component may, but neednot, be the same length as the second fiber component. When used in thepresent invention the first fiber component may be added to the hybridmixture in lengths of about 19 to about 60 mm. For example, in oneembodiment of the present invention, the first fiber component may beadded in lengths of about 54 mm.

The second fiber component is a high strength fibrous reinforcementcopolymer, such as, but not limited to, one formed of embossedmonofilaments. The second fiber component is preferably a copolymerformed of major amounts, preferably about 75–80 percent by weight,polypropylene, preferably a low melt polypropylene (2-melt homopolymer),and minor amounts, preferably about 20–25 percent by weight,high-density polyethylene. The second fibers do not fibrillate; i.e.,they do not pull apart to form a net like structure in the cementitiousmaterial.

The second fiber component is a high tenacity, polyolefinic threadhaving high resistance, and excellent flexibility. As incorporated inthe hybrid blend of the present invention, the second fiber componentincludes monofilaments of approximately 350 to about 6000 denier perfilament. The preferred embodiment of the second fiber component ispreferably twisted to form a non-interconnected bundle of multiplestrands of a nonfibrillating monofilament. In one embodiment of thepresent invention, the second fiber component exhibits the followingproperties:

PHYSICAL PROPERTIES OF THE SECOND FIBER COMPONENT Material VirginCopolymer Color Gray Form Collated Hybrid-Twisted Acid/Alkali ExcellentMonofilaments Resistance Specific 0.91 Absorption Nil Gravity Tensile70–106 ksi. (485–730 Mpa) Compliance A.S.T.M. C-1116 Strength Length 2¼″(54 mm)

For example, in one embodiment of the present invention, the secondcomponent is approximately 750 denier per filament. When used alone (notas a hybrid blend in combination with the first component, discussedabove, and disclosed herein), the second component is typically added ata dosage rate of about 4 to about 30 pounds per cubic yard (1.8 to 13.6kilograms per cubic meter) of cementitious material directly to themixing system during, or after, the batching of the other ingredientsand distributed therethrough. The resultant fiber reinforced materialexhibits long term durability. It should be noted, however, that thesecond fiber component, by itself, when not twisted, exhibits less thanoptimum distribution properties in the building material during mixingoperation. However, when the monofilaments of the second fiber componentare twisted, as used in the preferred embodiment of the synthetic fiberblend of the present invention, to form the non-interconnected bundle,the synthetic fiber blend is easier to mix and is uniformly distributedthroughout the cementitious material.

It has been found that when the second fiber component is twisted, thedegree of twist of the bundle is relevant to the distribution propertiesof the second fiber component in the building material in which it isadded. As set forth in FIG. 30, a single turn is identified as “x” and,as used herein, is defined as a full revolution (360°) along the linearlength of the fiber bundle. The number of turns per linear foot (turnsper linear inch or turns per linear centimeter), identified herein asturns/foot, turns/inch, or turns/cm, respectively, provides a pronounceddifference in the ability of the second fiber component to mix with, andbe more evenly distributed throughout, the building material. Thisdifference in distribution, in turn, is believed to account, at least inpart, for the increase in improved reinforcement properties exhibited bythe synthetic fiber blend of the present invention.

Early attempts at forming the synthetic fiber bundle of the presentinvention employed twisting the multiple strands of monofilaments toabout 9 turns/foot (about 0.75 turns/inch or about 0.3 turns/cm). Thisdegree of twist has been found to produce good mixing and distributionproperties throughout the cementitious material, as set forth herein.Additional testing indicated that similar results are obtained when thedegree of twist was increased to up to about 11 turns/foot (about 0.9turns/inch or about 0.36 turns/cm). Accordingly, twisting the fibercomponent in the range of about 0.75 turns/inch (about 0.3 turns/cm) toabout 0.9 turns/inch (about 0.36 turns/cm) has been found to provideimproved mixing and distribution properties throughout the buildingmaterials in which the second fiber component was added, relative tobuilding materials that do not employ embodiments of the untwisted fibercomponent of the present invention. It was noted, however, that when theindividual strands of monofilament were twisted in the range of about0.75 turns/inch (about 0.3 turns/cm) to about 0.9 turns/inch (about 0.36turns/cm), some splitting and “paint brush” effect were visible in theindividual strands of monofilaments. This commonly known effect 10 isillustrated in FIG. 31, and can adversely affect the ability of themonofilaments to disperse throughout the cementitious materials. Inaddition, it was found that at a degree of twist below about 0.9turns/inch (about 0.36 turns/cm) there was incomplete separation of themonofilaments from the fiber bundle. This was particularly evident incertain embodiments of the present invention that employ strands offilament, each strand comprising two or more connected monofilamentsthat are designed to break apart into individual monofilaments as aresult of the act of twisting the fiber strands into the twisted bundle.

It was found through experimental testing that a pronounced improvementin mixing and distribution resulted when the second component was formedwith a tighter twist above about 11 turns/foot (about 0.9 turns/inch orabout 0.36 turns/cm). These improved results were observed at a degreeof twist less than about 2.2 turns/inch (about 0.87 turns/cm), which isapproximately the highest degree of twist that an unheated fiber bundlecan be twisted without significant “spring back” effect (i.e. the effectwherein a fiber bundle untwists from its twisted form and, possibly,unbundles due to the resilient properties of the polymer). Typically,the improved properties in mixing and distribution as a result of thedegree of twist in the fiber bundle were measured at greater than about11 turns/foot (about 0.9 turns/inch or about 0.36 turns/cm), andtypically occurred in the range between greater than about 11 turns/foot(about 0.9 turns/inch or about 0.36 turns/cm) and about 13 turns/foot(about 1.1 turns/inch or about 0.43 turns/cm), and may occur at a degreeof twist of about 13 turns/foot (about 1.1 turns/inch or about 0.43turns/cm). Moreover, it was found that with an increase in the degree oftwist to greater than about 1 turns/inch (about 0.39 turns/cm), littleor no splitting or “paint brush” effect was observed in themonofilaments, and nearly all the individual monofilaments that formedthe fiber bundle completely separated from the bundle and were disbursedthroughout the building material in which it was added. This wasparticularly evident in certain embodiments of the present inventionthat employ strands of filament, each strand comprising two ore moreconnected monofilaments that are designed to break apart into individualmonofilaments as a result of the act of twisting the fiber strands intothe twisted bundle, ultimately forming the twisted bundle ofmonofilaments.

It is contemplated that some additional advantages may be obtained inthe mixing and distribution of the second fiber component when thetwisted fiber bundle configuration of the second fiber component isheated to below its melting point and twisted, which may allow the fiberbundle to be twisted to a degree of twist that is greater than about 2.2turns/inch (about 0.87 turns/cm). In this embodiment, the individualmonofilaments of the second fiber component may be heated, before orafter being formed into a twisted bundle, to, for example, up to about325° F. that may provide a fiber bundle having a degree of twist that isgreater than about 2.2 turns/inch (about 0.87 turns/cm) and that maysubstantially reduce or eliminate the spring back effect.

When used in the synthetic fiber blend of the present invention, thesecond fiber component may be added to the hybrid mixture in amounts ofabout 50 to about 95 by total weight percent. For example, in oneembodiment of the present invention, the second fiber component may beadded in amounts of about 93.3 total weight percent. In addition, thesecond fiber component may, but need not, be the same length as thefirst fiber component. When used in the present invention the secondfiber component may be added to the hybrid mixture in lengths of about19 to 60 mm. For example, in one embodiment of the present invention,the second fiber component may be added in lengths of about 54 mm.

The first fiber component and the second fiber component may be blendedin the amounts discussed above to form the hybrid fiber blend of thepresent invention. The first fiber component and the second fibercomponent may be blended by any means known in the art, such as, forexample, by combining the two fiber components in the cutting process.The hybrid fibers may be cut into useable strips either before of afterblending the first fiber component and the second fiber component. Whenthe hybrid fibers of the present invention are cut into useable stripsafter blending the first fiber component and the second fiber component,the hybrid fiber strips may be cut into any length that is dispersibleand pumpable, but may be cut into a length of about 19 to 60 mm, suchas, for example, a length of about 54 mm. It is contemplated that thefiber length may be adjusted according to specification. In one form ofthe present invention the resultant hybrid fiber has the followingphysical properties:

PHYSICAL PROPERTIES OF THE FIBER BLEND Material VirginPolypropylene/Virgin Color Gray Copolymer Form CollatedHybrid-Fibrillated/ Acid/Alkali Excellent Twisted Monofilament BundleResistance Fiber System Specific 0.91 Absorption Nil Gravity Tensile90–110 ksi. (620–758 Mpa) Compliance A.S.T.M. C-1116 Strength Length  ¾″(19 mm), 1½″ (38 mm), 2¼″ (54 mm), 2½″ (60 mm)

When incorporated into a building material such as concrete, the hybridfiber blend of the present invention may be added to the mixture inamounts ranging from about 0.1 percent to about 2.0 percent by volume ofconcrete, and typically in amounts ranging from about 0.5 to about 2.0percent by volume of concrete, to impart improved reinforcementcharacteristics thereto. The hybrid fiber blend may be added directly tothe mixing system during, or after, the batching of the otheringredients and mixed at the time and speed recommended by the mixermanufacturer (typically four to five minutes).

The hybrid fiber blend of the present invention may be used to reduceplastic and hardened concrete shrinkage and settlement shrinkage priorto initial set that leads to cracking. Furthermore, the hybrid fiberblend improves impact strength, and increases fatigue resistance andconcrete toughness as an alternate secondary/temperature/structuralreinforcement. Moreover, in addition to the twisting of the second fibercomponent, it has been found that the combination of the first fibercomponent with the second fiber component substantially increases theability of the second fiber component to be more evenly distributedthroughout the mixture. It is believed that the improved distributionproperties of the second fiber component, in part, account for theincrease in improved reinforcement properties exhibited by the syntheticfiber blend of the present invention. In addition, the fiber of thepresent invention is non-corrosive, non-magnetic, and substantiallyresistant to the effects of the alkaline nature of conventional buildingmaterials, such as, for example, Portland cement concrete.

As illustrated in the examples below, the present invention providesadvantages in cost, operation, and structural reinforcement over knownreinforcement components. The fiber component combination of the presentinvention, as compared to wire mesh or conventional steel fibers are notcorrosive, are easily mixed with the building material, reduce plasticshrinkage cracking, and provide cost efficiencies and structuraladvantages to the resultant formed material. The synthetic fibersreplace steel fibers for reinforcement of cementitious materials andeliminate the damage to equipment caused by steel fibers. When comparedto other synthetic fibers, the fibers of the present invention providemore effective mixing operation and increased structural advantages tothe building material in which they are added.

In order that those skilled in the art may better understand how theinvention may be practiced, the following examples are given by way ofillustration and not by way of limitation on the invention as defined bythe claims. As will be apparent upon inspection of the test resultsbelow, the synthetic hybrid fiber blend of the present inventionsubstantially and impressively improves the reinforcementcharacteristics of the building material to which it is added, ascompared to the conventional fiber reinforcement materials. A series oftests were performed to evaluate various amounts of a synthetic fiberblend of the present invention. The results are provided hereinbelow.

EXAMPLES Example 1

The hybrid synthetic fibers of the present invention were tested todetermine plastic shrinkage reduction of concrete using cement-richmixes, known to exhibit a high potential for shrinkage cracking. Thedosages of fiber used were 0.5, 1.0 and 2.0 percent by volume ofconcrete. Three different batches of concrete were made and a total of15 slabs were tested. The tests were conducted using a 2.0 inch (5.08cm) thick slab that was 3 feet (91.4 cm) long and 2 feet (61 cm) wide.The crack development was enhanced by using fans that can produce a windvelocity of 14 mph (22.5 km/hr). The performance of these fibers wascompared using the crack areas of control slab with no fibers and fiberreinforced slabs.

As illustrated below, the results of the tests indicate that the fibersof the present invention, at the dosages used, significantly reduced theplastic shrinkage in concrete. The crack area reduction varied from 100to 92 percent of the plain concrete. No cracking was observed when afiber dosage of 2.0 percent by volume of concrete was used. There was 98percent and 92 percent reduction of plastic shrinkage cracking when thefiber dosages were respectively 1.0 percent and 0.5 percent by volume ofconcrete.

Test Method

Tests were conducted using 2 inch (5.08 cm) thick slabs that were 3 feet(91.4 cm) long and 2 feet (61 cm) wide. The slabs were restrained aroundthe perimeter using wire meshes. After casting, the slabs were placed ona flat surface and subjected to a wind velocity of 14 mph (22.5 km/hr),using high-velocity fans.

The development of cracks were observed within two to three and one halfhours after casting. Although, typically, cracking is complete withinabout six to eight hours, the crack widths and lengths were measuredafter 24 hrs. The longer duration was chosen to ensure all cracksdeveloped and stabilized. The crack width was measured at a number oflocations along the length of the crack. The length of the crack wasmeasured for each crack and multiplied by the average width. Thus thetotal crack area for a given slab is calculated.

The control slab (no fibers) crack value was set at 100 percent. Thecrack area of the other panels was expressed as a percentage of thecontrol and the percent reduction of crack area due to the addition offibers is obtained.

Materials

The materials consisted of ASTM Type I cement, concrete sand and coarseaggregate. The coarse aggregate had a maximum size of 0.75 in. Both fineand coarse aggregates satisfied ASTM aggregate requirements.

The chemical and physical properties of the hybrid synthetic fibers usedwere those as described herein.

Mix Proportions

Because the objective of this test was to study the influence of fiberaddition on the plastic shrinkage, it was necessary to make the concretewith a very high potential for shrinkage cracking. The testingconditions, such as the ambient temperature, the humidity, and the windvelocity (14 mph) (22.5 km/hr) were kept constant for each batch. Threedifferent batches of concrete were made with the same water contents,cement contents and maximum size of coarse aggregates. A higher cementcontent was used, to increase the cracking potential. The basic mixtureproportion used was as follows:

Cement (lbs)   855 (388 kg) Water (lbs)   427 (194 kg) Water/CementRatio  0.5 Concrete Sand (lbs)  1062 (482 kg) Coarse Aggregates (lbs) 1062 (482 kg) Maximum Size of Aggregates (inches)  0.75 (1.91 cm)Mixing Procedure and Casting the Specimens

All mixing was done in a nine cubic feet capacity mixer. The fibers wereweighed and stored in a separate container. First the buffer mix wasprepared. Thereafter, coarse aggregates were introduced into the mixer.Sand and two thirds of the water were then added and mixed for oneminute. Cement was then added along with the remaining one third of thewater. Thereafter, the fibers of the present invention were added andthe ingredients were mixed for three minutes. Following mixing, themixture was subject to a three minute rest period, followed by a finalmixing stage for 2 minutes for proper fiber distribution.

Because the fiber reinforced cementitious mixes were of a flowingconsistency, both mixing and placing were carried out without anyproblems. No segregation or balling of the fibers was observed in any ofthe mixes. In order to maintain consistency in placing, consolidating,and finishing the slabs, an experienced concrete contractor and finisherperformed the placing, consolidating and finishing for all the slabs.

Three batches were made on three separate days. After each batch ofreinforced cementitious material was prepared, the mixing drum wasthoroughly cleaned. A buffer mix was prepared before preparing asubsequent mix. All of the mixes were prepared under identicalconditions.

Test Results and Discussion

Three cylinders were prepared for each of the six mixes with and withoutfibers according to the ASTM procedures. The cylinders were tested after14 days of curing. The results are provided in Table 1, below. Asillustrated in Table 1, the cylinder strengths in all the mixes wereconsistently close. The 14-day compressive strength results of all 18specimens were approximately the same.

The measured crack lengths, widths, and areas for the control and fiberreinforced slabs are given in Tables A1 to A3, B 1 and B2, and C1 to C2respectively for batches A, B, and C. Each table compares the mixesprepared on a particular day. The influences of various fiber dosages onthe plastic shrinkage cracking are shown in illustrated in FIGS. 1 to 6.The summary of the test results and the percentage reduction in plasticshrinkage cracking are given in Table 2. The comparison of variousparameters for different fiber contents is shown in Table 3.

Three specimens were tested for each of the three fiber contents and theaverage crack areas were calculated. The results of these calculationare provided in Table 2. Table 2 includes the average crack area of twocontrol slabs without fibers, as well as the crack areas of FRC, and areexpressed as the percent of the crack area of the control slabs and thepercentage reduction of the plastic shrinkage cracking due to theaddition of three fiber dosages.

FIGS. 1–4 graphically illustrate the crack areas of different fibercontents (FIG. 1), crack length of different fiber content (FIG. 2), thetime observed for crack formation based on fiber content (FIG. 3), andcrack areas between control slabs and reinforced fiber slabs (FIG. 4).An overall comparison of the plastic shrinkage crack reduction potentialof the three fiber contents is shown in FIGS. 5 and 6.

No cracks were observed in any of the three slabs reinforced with 2.0percent by volume of the synthetic fiber blend of the present invention.The results indicate that all three fiber contents were effective inreducing the plastic shrinkage cracking in concrete. However the amountof crack reduction is different for different fiber dosages. The crackreduction potential varies from about 92 to 100% for these fibercontents.

Conclusions

The test results on the control slabs and the fiber reinforced slabsconfirm that the fibers of the present invention are very efficient inreducing the plastic shrinkage cracking in concrete. The tests revealedthat even at very low addition levels, the synthetic hybrid fiber of thepresent invention provided extremely high crack reduction. At fiberdosages of 0.5 percent by volume, a crack reduction of 92% was achieved.At fiber dosages of 1.0 percent by volume, a crack reduction of 98% wasachieved. Furthermore, there was no observed plastic shrinkage crackingwhen 2.0% by volume of fibers were used.

TABLE 1 14-Day Compression Strength for Shrinkage Test Specimens BatchFiber Content Specimen Comp. Strength psi Average psi No. (% by Vol.)No. (kg/cm²) (kg/cm²) A 0 FEP1-1 4725.97 4740.38 (control) (332.27)(338.28) FEP1-2 4793.98 (337.98) FEP1-3 4701.19 (330.53) 1 FEF1-14722.22 4753.76 (332.01) (334.22) FEF1-2 4754.36 (334.27) FEF1-3 4784.69(336.40) B 0 FEP2-1 4754.36 4805.09 (control) (334.27) (337.83) FEP2-24833.59 (339.84) FEP2-3 4827.31 (339.39) 2 FEF2-1 4924.54 4944.47(346.23) (347.63) FEF2-2 4964.26 (349.02) FEF2-3 4944.62 (347.64) C 0FEP3-1 4793.97 4640.42 (control) (337.05) (326.25) FEP3-2 4361.62(306.65) FEP3-3 4765.68 (335.06) 0.5 FEF3-1 4733.49 4729.74 (332.80)(332.53) FEF3-2 4769.47 (335.33) FEF3-3 4686.25 (329.48)

TABLE 2 Plastic Shrinkage Reduction due to addition of Hybrid FiberBlend Crack Area Crack Area Crack Area Type (mm²) (% of Control)(Reduction %) BATCH A Control Slab 1 413.93 100 98 Control Slab 2 195.76Average 304.85 Hybrid Fiber 1% by Volume Slab 1 5.68 2 Slab 2 1.45 Slab3 13.06 Average 6.73 BATCH B Control Slab 1 373.81 100 100 Control Slab2 424.97 Average 399.39 Hybrid Fiber 2% by Volume Slab 1 No Crack 0 Slab2 No Crack Slab 3 No Crack BATCH C Control Slab 1 210.47 100 ControlSlab 2 175.07 Average 192.77 Hybrid Fiber 0.5% by Volume Slab 1 26.42 892 Slab 2 13.59 Slab 3 5.26 Average 15.09

TABLE 3 Comparison of Various Parameters for Different Fiber ContentsFiber Crack Crack Crack Time of Casting Conditions Slabs with LabContent Area Length Width First Crack Humidity Temperature Fiber Batch(% by Vol.) (mm²) (mm) (mm) L/W (min) (%) (Deg F.) Batch C 0.5 15.0947.10 1.02 46.176 170 38 75 Batch A 1.0 6.73 52.73 1.37 38.489 195 15104 Batch B 2.0 39 82 Crack Crack Crack Time of Casting ConditionsControl Lab Area Length Width First Crack Humidity Temperature SlabsBatch (mm²) (mm) (mm) L/W (min) (%) (Deg F.) Batch C 192.77 238.8 5.3544.67 120 38 75 Batch A 304.85 431.3 9.99 43.19 125 20 99 Batch B 399.39317.8 9.13 34.82 120 35 87 Notes: 1. The values under Crack area, Cracklength and Crack width for the slabs with fiber are the average ofvalues from three slabs. 2. The values under Crack area, Crack lengthand Crack width for the control slabs are the average of values from twoslabs. 3. All the three slabs in Batch B did not crack.

TABLE A1 Details of Crack Lengths, Widths & Areas; Batch A; ControlSlab 1. Avg. Crack Length Width Width Area No. (mm) (mm) (mm) (mm²) 111.20 0.50 0.59 6.61 0.80 0.80 0.45 0.40 2 6.70 0.35 0.28 1.84 0.35 0.250.15 3 6.80 0.50 0.55 0.55 0.80 0.80 0.50 0.15 4 11.90 0.80 0.51 6.070.80 0.50 0.30 0.15 5 10.90 0.45 0.26 2.83 0.10 0.15 0.45 0.15 6 12.700.30 0.36 4.55 0.45 0.50 0.45 0.15 0.30 7 115.20 0.80 1.87 215.7 0.802.00 2.00 1.00 3.00 3.00 3.00 2.00 2.00 1.00 7A 7.60 0.80 0.92 6.99 1.001.00 1.00 0.80 7B 19.30 0.80 0.82 15.83 1.00 1.00 0.80 0.50 7C 27.202.00 1.47 39.89 2.00 2.00 1.00 1.00 0.80 8 6.20 0.50 0.43 2.64 0.45 0.450.30 9 13.90 0.50 0.34 4.73 0.50 0.30 0.20 0.20 10 11.70 0.40 0.29 3.360.40 0.20 0.15 11 11.50 0.40 0.29 3.34 0.35 0.35 0.20 0.15 12 53.60 0.801.18 63.43 1.00 2.00 2.00 0.80 0.50 13 4.80 0.50 0.58 2.78 0.80 0.800.50 0.30 14 23.40 0.80 1.40 32.76 1.00 2.00 2.00 2.00 1.00 1.00 TotalArea 413.93

TABLE A2 Details of Crack Lengths, Widths & Areas; Batch A; Control Slab2. Avg. Crack Length Width Width Area No. (mm) (mm) (mm) (mm²) 1 19.600.80 0.84 16.42 1.00 1.00 1.00 0.80 0.80 0.80 0.50 2 38.40 0.40 1.0339.68 0.80 0.80 1.00 2.00 2.00 1.00 0.80 0.50 3 9.20 0.80 0.73 6.67 0.800.80 0.50 4 22.60 0.20 0.69 15.50 0.50 0.80 1.00 1.00 0.80 0.50 5 15.200.20 0.33 5.02 0.35 0.40 0.35 0.35 6 9.90 0.20 0.24 2.35 0.20 0.35 0.207 31.30 0.40 0.46 14.35 0.45 0.50 0.45 0.50 0.45 8 40.70 0.35 0.39 15.870.30 0.35 0.50 0.45 9 43.40 0.20 0.26 11.21 0.20 0.20 0.35 0.40 0.20 1015.20 0.20 0.20 3.04 0.20 0.20 0.20 11 23.40 0.40 0.36 8.42 0.45 0.450.30 0.20 12 54.40 0.20 0.28 14.96 0.20 0.20 0.30 0.45 0.45 0.20 0.20 1312.90 0.20 0.20 2.58 0.20 0.20 0.20 14 12.70 0.20 0.25 3.18 0.30 0.200.30 15 24.20 0.20 0.28 6.66 0.20 0.30 0.45 0.30 0.20 16 26.40 0.20 0.225.81 0.20 0.30 0.20 0.20 17 22.80 0.20 0.23 5.13 0.20 0.20 0.30 18 14.400.20 0.22 3.17 0.20 0.30 0.20 0.20 19 23.80 0.20 0.22 5.16 0.20 0.200.30 0.20 0.20 20 28.30 0.20 0.23 6.60 0.20 0.30 0.30 0.20 0.20 21 19.200.15 0.21 4.00 0.20 0.20 0.20 0.30 0.20 Total Area 195.76

TABLE A3 Details of Crack Lengths, Widths & Areas; Batch A; SlabsReinforced with Hybrid Fiber Blend (1%) Avg. Crack Length Width WidthArea No. (mm) (mm) (mm) (mm²) Slab 1 1 6.30 0.20 0.18 1.13 0.15 0.200.20 0.15 2 3.90 0.20 0.23 0.88 0.30 0.20 0.20 3 4.20 0.15 0.19 0.790.20 0.20 0.20 4 5.50 0.20 0.25 1.38 0.30 0.30 0.20 5 8.20 0.20 0.181.50 0.15 0.15 0.20 0.20 0.20 Total Area 5.68 Slab 2 1 8.60 0.20 0.201.72 0.25 0.15 0.20 2 7.70 0.15 0.21 1.62 0.20 0.30 0.20 0.20 3 19.900.20 0.22 4.38 0.20 0.20 0.30 0.20 4 7.90 0.20 0.22 1.74 0.30 0.20 0.200.20 5 10.60 0.15 0.21 2.23 0.20 0.30 0.20 0.20 6 5.90 0.20 0.18 1.030.20 0.15 0.15 7 5.50 0.15 0.21 1.16 0.30 0.20 0.20 0.20 Total Area 1.45Slab 3 1 5.70 0.15 0.19 1.08 0.20 0.20 0.20 0.20 2 6.40 0.30 0.21 1.340.20 0.20 0.15 0.20 3 5.40 0.20 0.21 1.13 0.30 0.20 0.20 0.15 4 10.600.25 0.26 2.76 0.30 0.20 0.30 0.25 5 14.20 0.15 0.17 2.41 0.20 0.20 0.150.15 6 5.60 0.30 0.24 1.34 0.30 0.20 0.20 0.20 7 8.70 0.30 0.19 1.650.20 0.15 0.15 0.15 8 7.40 0.20 0.18 1.33 0.20 0.15 0.20 0.15 Total Area13.06

TABLE B1 Details of Crack Lengths, Widths & Areas; Batch B; ControlSlab 1. Average Crack Length Width Width Area No. (mm) (mm) (mm) (mm²) 166.90 0.40 1.13 75.45 0.80 1.00 2.00 2.00 2.00 1.00 0.45 0.50 2 57.801.00 1.87 107.89 2.00 2.00 2.00 3.00 3.00 2.00 1.00 0.80 3 40.70 0.801.20 48.84 1.00 2.00 2.00 0.80 1.00 0.80 4 32.40 1.00 1.76 56.88 2.002.00 3.00 3.00 2.00 1.00 1.00 0.80 5 55.80 0.80 1.08 59.99 1.00 1.001.00 2.00 1.00 1.00 0.80 6 13.40 0.80 0.82 10.99 1.00 1.00 0.80 0.50 75.20 0.45 0.33 1.72 0.30 0.30 0.35 0.25 8 10.30 0.30 0.37 3.81 0.45 0.500.30 0.30 9 26.30 0.20 0.23 6.14 0.30 0.30 0.20 0.20 0.20 10 8.80 0.200.24 2.11 0.20 0.30 0.30 0.20 Total Area 373.81

TABLE B2 Details of Crack Lengths, Widths & Areas; Batch B; Control Slab2. Average Crack Length Width Width Area No. (mm) (mm) (mm) (mm²) 161.60 1.00 1.88 115.50 2.00 2.00 2.00 2.00 3.00 2.00 1.00 2 9.40 0.800.64 5.99 0.80 0.50 0.45 3 19.30 0.45 0.42 8.04 0.50 0.50 0.50 0.30 0.254 25.40 0.80 0.63 16.09 1.00 0.80 0.50 0.40 0.30 5 80.60 1.00 2.09168.53 1.00 2.00 3.00 1.00 3.00 3.00 3.00 3.00 2.00 1.00 5A 20.10 2.002.17 43.55 3.00 2.00 2.00 2.00 2.00 6 71.60 0.50 0.81 58.30 0.80 1.001.00 0.80 0.80 0.80 7 16.70 0.45 0.30 5.01 0.45 0.20 0.20 0.20 8 13.200.50 0.30 3.96 0.30 0.20 0.20 0.30 Total 424.97 Area

TABLE C1 Details of Crack Lengths, Widths & Areas; Batch C; ControlSlab 1. Average Crack Length Width Width Area No. (mm) (mm) (mm) (mm²) 149.90 0.80 1.20 59.88 1.00 1.00 2.00 2.00 0.80 1.00 1.00 2 46.40 1.001.37 63.63 2.00 2.00 2.00 1.00 0.80 0.80 2A 20.70 0.80 0.54 11.18 0.800.50 0.40 0.20 2B 14.20 0.50 0.36 5.11 0.50 0.30 0.30 0.20 3 15.60 0.500.47 7.28 0.80 0.50 0.50 0.30 0.20 4 68.60 0.80 0.70 48.02 1.00 1.001.00 0.80 0.50 0.30 0.20 5 19.70 0.20 0.31 6.19 0.40 0.50 0.50 0.20 0.200.20 6 11.40 0.20 0.26 2.96 0.40 0.30 0.20 0.20 7 15.30 0.20 0.22 3.320.20 0.30 0.20 0.20 0.20 8 11.60 0.30 0.25 2.90 0.20 0.40 0.20 0.20 0.20Total 210.47 Area

TABLE C2 Details of Crack Lengths, Widths & Areas; Batch C; Control Slab2. Average Crack Length Width Width Area No. (mm) (mm) (mm) (mm²) 120.10 0.20 0.30 6.03 0.30 0.40 0.50 0.20 0.20 2 16.60 0.20 0.27 4.430.40 0.30 0.30 0.20 0.20 3 19.70 0.20 0.30 5.91 0.40 0.40 0.40 0.20 0.300.20 4 10.20 0.20 0.23 2.38 0.30 0.30 0.20 0.20 0.20 5 29.40 0.50 0.319.24 0.40 0.30 0.40 0.20 0.20 0.20 6 63.20 1.00 2.10 132.72 2.00 3.002.00 2.00 3.00 3.00 2.00 2.00 1.00 6A 11.40 0.20 0.24 2.74 0.30 0.300.20 0.20 6B 12.80 0.40 0.37 4.75 0.50 0.80 0.30 0.20 0.20 0.20 6C 15.400.20 0.22 3.34 0.20 0.30 0.20 0.20 0.20 6D 5.30 1.00 0.67 3.53 0.80 0.800.50 0.50 0.40 Total 175.07 Area

TABLE C3 Details of Crack Lengths, Widths & Areas; Batch C; SlabsReinforced with Hybrid Fiber Blend (0.5%) Avg. Crack Length Width WidthArea No. (mm) (mm) (mm) (mm²) Slab 1 1 5.30 0.20 0.22 1.17 0.30 0.200.20 0.20 2 24.70 0.20 0.25 6.18 0.30 0.30 0.20 0.20 0.30 3 32.30 0.500.51 16.61 0.80 0.80 0.50 0.40 0.30 0.30 4 6.40 0.30 0.23 1.44 0.20 0.200.20 5 4.30 0.20 0.24 1.03 0.20 0.30 0.30 0.20 Total Area 26.42 Slab 2 16.60 0.20 0.26 1.72 0.30 0.40 0.20 0.20 2 14.40 0.30 0.38 5.52 0.50 0.500.50 0.20 0.30 3 25.40 0.30 0.25 6.35 0.30 0.30 0.20 0.20 0.20 Total13.59 Area Slab 3 1 6.70 0.20 0.22 1.452 0.20 0.20 0.30 0.20 0.20 2 7.400.20 0.23 1.727 0.20 0.30 0.30 0.20 0.20 3 7.80 0.30 0.27 2.08 0.30 0.400.20 0.20 0.20 Total 5.258 Area

Example 2

A study was conducted to evaluate the reformulated experimentalsynthetic hybrid fiber of the present invention at three addition ratesin wet-mix shotcrete. The discrete fibers were approximately 60 mm longby 0.3 mm thick by 0.3 mm wide. The fibrillating fiber was collated. Thefibers had a specific bulk density of 910 kg/m³.

Three shotcrete mixtures with nominally 1.0, 1.5, and 2.0% by volumefiber addition rate were produced for the purpose of the evaluation. Inall mixes, the collated fibrillating fibers were proportioned for 0.1%by volume addition rate, and the balance being the discrete 60 mm longfiber. The three mixtures were tested for fresh shotcrete properties,rebound data were determined, and one standard ACI shotcrete test panel,one Australian Round Panel and one South African Panel per mixture wereproduced.

Three beams for ASTM C1018 beam testing were diamond saw cut from eachstandard ACI shotcrete test panel. Cores were also extracted from thesetest panels for the determination of compressive strength. Permeabilitydata were determined on diamond saw cut beam ends. The South AfricanPanels were tested with uniformly distributed loading on a water bedtest assembly, while the Australian Round Panels were tested in centrepoint loading with determinate support at three points on custom builttesting machine made by AGRA Earth & Environmental Limited, Burnaby,B.C., Canada.

Shotcrete Mixture Design and Batching

The base wet-mix shotcrete mixture design used is shown in the table inTechnical Report No. 1, below. This mixture design is similar tomixtures typically used for permanent shotcrete linings in tunnels andmines, slope stabilization and infrastructure rehabilitation projects inNorth America. In the ternary blend of cementing material (portlandcement, fly ash and silica fume) the silica fume enhances adhesion andcohesion of the mix and reduces rebound; the fly ash increases pastevolume which improves pumpability and shootability.

In order to maintain tight control over mixture proportions, the baseshotcrete mix was drybatched. Bone-dry materials were used and all theingredients were precision mass batched with monitoring. The materialswere premixed in a rotary pan mixer with counter rotating paddles,before being discharged into 30 kg paper bags. Shotcrete was supplied onpallets and protected by shrink-wrap and covered under tarps formoisture protection prior to use.

Shotcrete was batched in a modified Allentown Powercrete Pro mixer unit,attached to a 75 mm swing valve pump. Typically fourteen, 30 kg bagswere batched at a time. Water was added to maintain a constantwater/cement ratio between all mixes. The fibers were added directly tothe mixer unit during the mixing cycle and mixed for approximately 5minutes to provide uniform fiber distribution prior to shotcretedischarge.

The following mixtures were produced: 1) Mixture F10 (nominally 1.0% byvolume fiber content); 2) Mixture F15 (nominally 1.5% by volume fibercontent); and 3) Mixture F20 (nominally 2.0% by volume fiber content,increased paste volume).

The superplasticizer dosage was adjusted as necessary to provide therequired slump for shooting. Mix F20 received a supplementary dose offly ash and water to increase the paste volume in order to maintain goodpumping properties in spite of the high fiber addition rate. Actualadmixture dosages for the three mixtures are shown in Technical ReportsNo. 1a to 1c, below.

Shotcrete Plastic Properties

1. Slump and Air Content

Details regarding the prevailing ambient conditions (temperature, windspeed, precipitation) and plastic shotcrete properties are given in thetable in Technical Report No. 2, below. The dosages of the admixturesrequired to produce the desired slump and as-batched air content arealso shown in this table. The table in Report No. 2 also detailsproperties of the as-batched and as-shot fresh shotcrete, and theoperating hydraulic pressure of the shotcrete pump as a measure of easeof pumping.

Slumps of the different mixtures ranged from 30 to 50 mm. As-batched aircontents of the mixtures, as discharged into the shotcrete pump, variedbetween 8 and 9%. For the determination of the as-shot air content, theshotcrete was shot into an ASTM C231 air pressure meter base. Theas-shot air content was in the 2 to 3% range. This is a higher thanusual loss of air content indicating that the fibers help entrap airwhich releases upon impact when the shotcrete is placed.

2. Pumpability and Shootability

The as-batched shotcrete was discharged into the pump hopper of the pumpprovided by Polycrete Restorations Ltd. The pump had a 75 mm diameterswing valve which discharged into a 50 mm internal diameter 15 m longhose and through a metal reducing section to a 38 mm internal diameter,30 m long hose when shooting mixtures F10 and F15. The respective hoselengths were approximately 8 m (50 mm diameter) plus 20 m (38 mmdiameter) when shooting mixture F20.

The table in Technical Report No. 2 shows that the mixtures requiredbetween 11 and 13 MPa hydraulic operating pressure of the pump to beshot, which is considered an acceptable pressure. The shotcrete pumpused in this testing program had a maximum operating pressure ofapproximately 16 MPa. The mixture with nominally 2.0% by volume fibertype F20 could be pumped generally satisfactory after the addition ofthe fly ash and water described above. Mix F20, however, approached thelimit of pumpability with the existing equipment and modified basemixture. Several blockages of the shotcrete hoses occurred due topressure-induced paste starvation near the 50 mm to 38 mm reducer piecewith mix F20.

All fibers dispersed well in the shotcrete. No balling was observed. Theshotcrete mixes adhered well to the substrates to which they wereapplied and did not slough.

3. Rebound Testing

Rebound testing was conducted on all mixes in a 2.5 m cube timber framedbox, lined with form-ply, open on one vertical face. Shotcrete wasapplied on a vertical face at the back of the box to an area about600×600 square×100 mm deep, with four shooting nails demarcating theshooting area. Material which fell to the floor of the rebound chamberwas recovered and weighed as rebound. The in-place material was thenremoved and weighed. Fiber wash-out testing was conducted on the entirerebound sample and on a representative sample of similar mass, takenfrom the in-place material. The following parameters were calculated: 1)as batched fiber content in kg/m³, percent by volume and percent bymass; 2) in-place fiber content in kg/m³, percent by volume and percentby mass; 3) fiber in rebound in kg/m³, percent by volume and percent bymass; 4) fiber rebound (=mass of all rebounded fibers/mass of allbatched fibers×100%); and 5) fiber retention (=in-place fibercontent/as-batched fiber content×100%).

Test results are provided in the attached Technical Report No. 3, below.The total rebound of shotcreting materials varied from 12 to 19% bymass, which is not atypical for shotcrete with a high content ofsynthetic fibers. A trend towards increasing rebound with increasingfiber addition rate was observed. The fiber retention varied from 94%for the mix with nominally 1.0% by volume of fiber addition rate toapproximately 80% for the other two mixes. This is a relativelyfavorable fiber retention and consistent with the rebound behavior ofother high volume synthetic fiber shotcretes tested elsewhere.¹ ¹Morgan,D. R., Heere, R., McAskill, N., Chan, C.: Comparative Evaluation ofSystem Ductility of Mesh and Fiber Reinforced Shotcrete, presented atEngineering Foundation, Shotcrete for Underground Support VIIIConference, Campos do Jordão, Brazil, 11–15 Apr. 1999

Shotcrete Production

1. ACI Test Panels

One standard 600×600×125 mm test panel per mix was shot at a slightlyinclined angle from vertical. The panels had 45° sloped edges tofacilitate escape of rebound and stripping of the panel from the form.The panels were moist cured in the field under plastic sheeting for 2days. At that time, core specimens for compressive strength testing andASTM C642 boiled absorption and volume of permeable voids testing wereprocured by diamond coring from these panels. In addition, a set ofthree 100×100×350 mm beams for toughness testing per ASTM C1018 werediamond saw cut from these panels. The specimens were moved to the fogroom in the laboratory at age 4 days, where they were moist cured at23+/−2° C. until the time of testing.

2. Australian Round Panel Test

One Australian Round Panel was shot for each mixture. The panels had adiameter of 800 mm and were approximately 80 mm thick. After shooting,the panel surface was struck off with a wooden two-by-four and finishedto a smooth finish with a steel trowel. The panels were moist curedunder plastic sheeting in the field for 4 days, then moved into the fogroom and stored at 23+/−2° C. and 100% Relative Humidity until the timeof testing.

3. South African Water Bed Test

One test panel with dimensions of 1600×1600×80 mm thick was shot foreach mixture. Void formers were placed at 1000 mm apart, i.e. at thelocations where rock bolts would penetrate to restrain the panel fromfree vertical movement during the test on the water bed station. Thepanel was shot in a vertical orientation and finished to an equivalentto cast-concrete surface finish, using a two-by-four for strike-off andsteel trowel finishing.

After initial set, the shotcrete panels were covered with plastic sheetsand kept moist and protected for 7 days. The panels were stripped fromthe forms at age 21 days and allowed to field cure for a further 8 daysprior to testing at age 28 days.

Hardened Shotcrete Properties

1. ASTM Standard Tests

a. Compressive Strength

Six, 75 mm diameter by about 110 mm long cores were extracted from eachof the standard ASTM test panels and tested for compressive strength toCSA A23.2–14C (which is equivalent to ASTM C42). Test results are givenin Technical Reports No. 4, below. All three shotcrete mixtures achievedapproximately 48 MPa compressive strength at 7 days. The following tableshows the ratio of achieved vs. predicted (based on the mixtureproportions and as-shot air content) compressive strength to illustrateany influence of the fiber addition rate on the compressive strength ofthe mixture.

Volumetric Predicted Achieved Ratio Achieved Fiber CompressiveCompressive vs. Predicted Addition Strength Strength Compressive MixtureRate (Popovic) [MPa] [MPa] Strength F10 1.0% 50 at 7 d 48 at 7 d  95%F15 1.5% 50 at 7 d 48 at 7 d  96% F20 1.9% 45 at 7 d 48 at 7 d 106%No clear effect of fiber addition rate on compressive strength wasevident.

b. Boiled Absorption and Volume of Permeable Voids

The results of the tests conducted on three beam-end saw-off portions at10 days are given in the attached Technical Report No. 5, below. Thevalues of Boiled Absorption ranged from 4.4% to 4.9%, and the Volume ofPermeable Voids ranged from 9.5% to 10.6%. These results are very lowcompared to the maximum limits of 8.0% for Boiled Absorption and 17.0%for Volume of Permeable Voids commonly specified for structural qualityshotcrete. These results are indicative of dense and durable shotcreteof low permeability.

c. Flexural Strength and Toughness

Flexural strength and toughness tests were conducted per ASTM C1018² forall mixtures at 7 days on sets of three nominally 100×100×350 mm beams,tested on a 300 mm load span with third point loading. Results of thetests are given in FIGS. 15–26 and tabulated in Technical Reports Nos.6a to 6f, below. The results show the first crack and ultimate flexuralstrength and the ASTM C1018 toughness indices and Residual StrengthFactors calculated from these indices. Also shown are the JapaneseToughness Parameters and Toughness Performance Levels³. ²With theexception of an open-loop control loading regime³Morgan, D. R., Chen,L., and Beaupré, D., Toughness of Fiber reinforced Shotcrete, ASCE

The results show that there was some instability in the load versusdeflection response at deformations up to about 0.5 mm. This isprimarily attributed to operation of the test machine in the open loopmode. The following table summarizes the flexural strength and toughnessproperties of the three mixtures tested.

Fiber Type and Ratio As-Batched Average Flexural vs. Japanese VolumetricFlexural Compressive Toughness Toughness Addition Strength StrengthFactor Performance Mixture Rate [MPa] at 7 Days [MPa] Level F10 2^(nd)6.8 14% 1.7 III generation, 1.0% F15 2^(nd) 6.1 13% 2.4 III generation,1.5% F20* 2^(nd) 6.1 13% 4.0 IV generation, 1.9% F2** 1^(st) 6.5 12% 4.1IV generation, (at 8 days) 2.0% *This mixture was produced with anincreased fly ash content **Mix F2 was previously produced and tested atAGRA, see our Report VA04526

The flexural strengths of the mixtures exceeded the frequently specifiedminimum of 4 MPa for shotcrete construction projects in Western Canada.The Japanese Toughness Factors and Toughness Performance Levels forshotcrete show a good correlation between fiber dosage and ductility.The fibers performed at a relatively high level and developed good bondwith the cement matrix. The fibers also developed most of theirload-carrying capacity as indicated by numerous ruptured fibers in thefractured faces.

2. Australian Panel Test

The Australian Round Panels were tested on a Round Panel Testing machineat age 7 days. The panels was statically determinately supported onthree swiveling supports with minimum constraint to radial movement (inthe horizontal plane). The central deflection of the panels was measuredwith a lever mounted LVDT, while the load was determined with a 80 kNload cell. A computer continuously logged the test data. For a moredetailed description of the test apparatus and test method, seeReference 1. FIGS. 27–29 provide the load deflection plot and TechnicalReport No. 7, below, provides the test results.

The following table summarizes important test data and compares them topublished data of shotcrete reinforced with commercially availablesynthetic fibers.

(Reference 1)

Absorbed As-batched Maximum Energy Fiber Peak Post-Crack (0–40 mm VolumeLoad Load Deflection) Specimen Dosage [kN] [kN] [Nm] or [J] Forta - F101.0% 31.2 16.8 525 Forta - F15 1.5% 29.8 20.0 640 Forta - F20 1.9% 27.925.2 750 S152-HPP 1.0% 34.7 15.2 290 Italics: Data from reference infootnote 1, test age >28 days

Test results showed that increasing the addition rate of fibers or thepresent invention reduces the ultimate load capacity of the shotcrete.An increase in the as-batched present invention fiber volume additionrate from 1.0% to 1.5% and 1.9% by volume increased the maximumpost-crack load of the specimens by 20% and 50% respectively, andincreased the overall absorbed energy to 40 mm central deflection by 22%and 43% respectively. Shotcrete for Underground Support VII, Telfs,Austria, 1995,pp. 66–87

The test results further showed that when compared to the SyntheticIndustries S-152HPP fiber, the hybrid synthetic fibers of the presentinvention provide superior performance at 1.0% volume addition rate.

3. South African Water Bed Test

The 1600×1600×76 mm panels were tested on AGRA's water bed reactionframe, adapted from the South African Water Bed Test developed byKirsten⁴. The test set-up comprises a reinforced concrete pedestal witha steel confined reinforced rubber water bed, high tensile strengthreaction bolts, and 100×100×10 mm rock bolt plates. The reaction bolts,which simulate rock bolts, were located on a 1000 mm square grid. Thefour cantilevered edges of the panels were supported against downwardmovement by four square hollow section steel profiles positioned bypairs of hydraulic jacks. ⁴Kirsten H.A.D., System Ductility of LongFiber Reinforced Shotcrete, Report prepared for shotcrete Working Group,South Africa, June 1997, pp. 27 and appendices.

The center point deflection of the panels was measured by means of aretracting extensometer mounted on an aluminum bridge and attached to anepoxy glued hook at the center of the panel. A pressure transducercontinuously monitored the water pressure in the water bed, which iscorrelated to the load applied to the shotcrete test panel. A computercontinuously recorded the load and deflection signals. The data werethen analyzed and used to plot the load versus deflection curves. Theelectronically monitored data were verified by mechanical measurementsof deflection (measuring tape) and water pressure (analog pressuregauge). Application of load to a total deformation of 150 mm took atotal of about 40 minutes.

In addition to continuously monitoring the load versus centraldeflection response of the panel, the sequence of crack formation wasrecorded. Crack width development with increasing deflection was alsorecorded.

Conclusions

The test results outlined above indicate that the hybrid fiber of thepresent invention displays surprisingly good physical properties overknown reinforcement fibers. The hybrid fibers of the present invention(60 mm long) could be batched, pumped and shot with standard shotcretingequipment using 38 mm internal diameter nozzle and as-batched fiberaddition rates of 1.0 to 1.9% by volume. The fiber dosage utilized inthis study appeared to not significantly affect the compressivestrength, flexural strength and values of boiled absorption and volumeof permeable voids of the shotcrete compared to a plain shotcrete mix.There did, however, appear to be a trend towards a reduced pre-crackingload carrying capacity of the round shotcrete panels with increasedfiber addition rate. Test results show that the fibers can develop theirfull tenacity (tensile strength capacity) in high quality shotcrete. Inaddition, the bond between the fibers and the shotcrete matrix appearedto be sufficient to prevent fiber pull-out of a majority of the fibersspanning a crack. Moreover, the overall ductility of the shotcretereinforced with 1.0 to 1.9% by volume of the hybrid fibers appeared tobe comparable with other, commercially available high-performancemonofilament synthetic fibers. Moreover, tests results show that theshotcrete with 1.0% by volume hybrid fiber provides toughness and systemductility that appears to be acceptable for shotcrete construction workrequiring a moderate resistance to post-cracking loads, as in someground support and slope stabilization projects, and in construction oferosion control in creeks, river banks and dams. The shotcrete with 1.5%by volume hybrid fiber provides toughness and system ductility thatappears to be equivalent to some high quality steel fiber or welded wiremesh reinforced shotcretes, especially at larger crack widths. Inaddition, the shotcrete with 1.9% by volume hybrid fiber providestoughness and system ductility that appears to perform equivalent orbetter than some high quality steel fiber and welded wire meshreinforced shotcretes, especially at larger crack widths.

TECHNICAL REPORT No. 1 SUBJECT: Base Wet-Mix Shotcrete MixtureProportions, SSD Condition Mass Bulk Density Volume Material [kg][kg/m³] [m³] Cement Type 10 400 3150 0.1270 Silica Fume 45 2200 0.0205Fly Ash 30 2200 0.0136 Coarse Aggregate (10–2.5 mm), 500 2650 0.1887 SSDSand (SSD) 1130 2650 0.4264 Water (estimate) 180 1000 0.1800 WaterReducing Admixture: 1.40 1000 0.0014 Masterbuilder ® Pozzolith ® 325-NSuperplasticizer: Masterbuilder ® 2.00 1000 0.0020 Rheobuild ® 3000 [L]*Air Entraining Admixture: 0.40 1000 0.0004 Masterbuilder ® Microair ®Air Content as shot 4.0% 0.0400 Total 2288.4 1.0000 Specified 28 DayStrength = 40 MPa W/(C + SiF + FA) Ratio = 0.38 Slump (aftersuperplasticizer and fiber addition) = 70 ± 20 mm

TECHNICAL REPORT No. 1a SUBJECT: As-Batched Shotcrete MixtureProportions Batch Identification: F10 Calculated Fiber Content [% byvol.]: 1.01% Batch Size (bags): 14 water/cementing materials ratio: 0.33Water, Base Admixtures, shotcrete Fibers, Calculated mass per Fly ashBulk SSD batch, added, Density Mass bone dry per batch [SSD] per m³Material [kg] [kg] [kg/m³] [kg] Cement Type 10 81 0 3150 414 Silica Fume9 0 2200 47 Fly Ash 6 0 2200 31 Coarse Aggregate 100 0 2650 517 (10–2.5mm) Sand 224 0 2650 1169 Water 35.8 1000 165 Synthetic Fibers, 1.790 9109.2 FORTA ® 1.0% Water Reducing 0.295 1.52 Admixture (Pozzolith ® 325-N)[L] Superplasticizer 0.200 1.03 Rheobuild ® 3000 [L]* Air Entraining0.090 0.46 Admixture (Microair ®) [L] Air Content At Pump 8.9% As Shot1.9% 1.9% Total 420 2355

TECHNICAL REPORT No. 1b SUBJECT: As-Batched Shotcrete MixtureProportions Batch Identification: F15 Calculated Fiber Content [% byvol.]: 1.51% Batch Size (bags): 14 water/cementing materials ratio: 0.33Water, Base Admixtures, shotcrete Fibers, Calculated mass per Fly ashBulk SSD batch, added, Density Mass bone dry per batch [SSD] per m³Material [kg] [kg] [kg/m³] [kg] Cement Type 10 81 0 3150 412 Silica Fume9 0 2200 46 Fly Ash 6 0 2200 31 Coarse Aggregate 100 0 2650 514 (10–2.5mm) Sand 224 0 2650 1162 Water 35.8 1000 164 Synthetic Fibers, 2.685 91013.7 FORTA ® 1.5% Water Reducing 0.360 1.84 Admixture (Pozzolith ®325-N) [L] Superplasticizer 0.100 0.51 Rheobuild ® 3000 [L]* AirEntraining 0.090 0.46 Admixture (Microair ®) [L] Air Content At Pump8.0% As Shot 2.0% 2.0% Total 420 2345

TECHNICAL REPORT No. 1c SUBJECT: As-Batched Shotcrete MixtureProportions Batch Identification: F20 Calculated Fiber Content [% byvol.]: 1.90% Batch Size (bags): 14 water/cementing materials ratio: 0.34Water, Base Admixtures, shotcrete Fibers, Calculated mass per Fly ashBulk SSD batch, added, Density Mass bone dry per batch [SSD] per m³Material [kg] [kg] [kg/m³] [kg] Cement Type 10 81 0 3150 390 Silica Fume9 0 2200 44 Fly Ash 6 10 2200 78 Coarse Aggregate 100 0 2650 487 (10–2.5mm) Sand 224 0 2650 1100 Water 39.8 1000 174 Synthetic Fibers, 3.580 91017.3 FORTA ®2.0% Water Reducing 0.360 1.74 Admixture (Pozzolith ® 325-N)[L] Superplasticizer 0.100 0.48 Rheobuild ® 3000 [L]* Air Entraining0.090 0.44 Admixture (Microair ®) [L] Air Content At Pump 8.6% As Shot2.6% 2.6% Total 420 2293

TECHNICAL REPORT No. 2 SUBJECT: Site Conditions and Fresh ShotcreteProperties Mix Identification Property Unit F10 F15 F20 As-batched FiberContent % by vol. 1.01  1.51 1.90 Water Reducer Addition Rate L/m³ 1.52 1.84 1.74* Superplasticizer Addition Rate L/m³ 1.03  0.51 0.48* AirEntraining Agent Addition Rate L/m³ 0.46  0.46 0.44 Ambient Temperature° C. 21 21 22 Ambient Wind Speed (estim.) m/s 2  1 2 Precipitation 0  00 AS-BATCHED Slump (with Fibers and HRWR) mm 50 30 50 Air Content (withFibers and HRWR) % 8.9  8.0 8.6 Shotcrete Temperature ° C. 24 26 28AS-SHOT Pumping Pressure (hydraulic circuit) MPa 11 13 11 Air Content %1.9  2** 2.6 n.a. = Not Available *mix contains additional fly ash andwater for enhanced pumpability **estimate based on the as-batched aircontent

TECHNICAL REPORT NO. 3 SUBJECT: Shotcrete and Fiber Rebound TotalRebound As-batched Fiber Content In-place Fiber Content Fiber in ReboundFiber Mix Mix (% by (% by (% by (% by (% by (% by (% by Retention No.Description mass) (kg/m³) vol) mass) (kg/m³) vol) mass) (kg/m³) vol)mass) (%) F10 1.0% Hybrid 12.2 9.1 1.0 0.39 8.5 0.94 0.37 21.2 2.33 0.9294 Fiber F15 1.5% Hybrid 17.3 13.7 1.5 0.59 10.7 1.18 0.46 28.7 3.161.24 78 Fiber F20 2.0% Hybrid 19.0 18.2 2.0 0.79 14.4 1.58 0.62 34.73.82 1.50 79 Fiber

TECHNICAL REPORT No. 4a HYBRID FIBER SHOTCRETE EVALUATION SUBJECT:Compressive Strength of Cored Shotcrete Specimens to CSA A23.2-14CCalculated Average Source, Shotcrete Age Compressive CompressiveLocation [days] Strength [MPa] Strength [MPa] Panel F10 7 50.9 47.6 45.047.0 Panel F15 7 47.6 47.7 47.5 48.0 Panel F20 7 48.8 48.1 45.0 50.3Core Diameter [mm] = 75

TECHNICAL REPORT No. 5 SUBJECT: ASTM C642 Boiled Absorption and Volumeof Permeable Voids Absorption Bulk Specific Absorption after Volume ofGravity after after Immersion Permeable Immersion Specimen Immersion andBoiling Voids and Boiling Identification [%] [%] [%] [kg/m³] F10A 4.54.7 10.6 2345 F10B 4.0 4.2 9.6 2370 F10C 4.0 4.3 9.8 2368 Average 4.14.4 10.0 2361 F15A 4.5 4.8 9.0 1956 F15B 4.6 5.0 8.2 1735 F15C 4.6 5.111.2 2329 Average 4.6 4.9 9.5 2007 F20A 4.4 4.9 10.9 2331 F20B 4.3 4.910.8 2330 F20C 4.2 4.5 10.1 2340 Average 4.3 4.8 10.6 2333

TECHNICAL REPORT No. 6a SUBJECT: ASTM C1018 Toughness Parameters andResidual Strength Factors Fiber Type: Hybrid Synthetic Fibers FiberAddition Rate: 1.0% by vol. First-Crack Ultimate Toughness ResidualStrength Sample Strength Strength Indices Factors No. (MPa) (MPa) I₁₀I₃₀ I₆₀ R_(10,30) R_(30,60) F10A 6.62 6.62 N.A. 8.6 18.7 N.A. 33.7 F10B6.50 6.50 N.A. 7.0 16.1 N.A. 30.3 F10C 7.17 7.17 N.A. 4.8 11.3 N.A. 21.7Avg. 6.77 6.77 N.A. 6.8 15.4 N.A. 28.6 N.A. = not available due to largeinitial deformations after first-crack

TECHNICAL REPORT No. 6b SUBJECT: Japanese Toughness Parameters andToughness Performance Levels Fiber Type: Hybrid Synthetic Fibers FiberAddition Rate: 1.0% by vol. Japanese Toughness Parameters First-CrackUltimate Toughness Toughness Sample Strength Strength Toughness FactorPerformance No. (MPa) (MPa) (kN · mm) (MPa) Levels F10A 6.62 6.62 13.82.08 III F10B 6.50 6.50 12.2 1.79 III F10C 7.17 7.17 9.2 1.35 II–IIIAvg. 6.77 6.77 11.7 1.74 III

TECHNICAL REPORT No. 6c SUBJECT: ASTM C1018 Toughness Parameters andResidual Strength Factors Fiber Type: Hybrid Synthetic Fibers FiberAddition Rate: 1.5% by vol. First- Crack Ultimate Toughness ResidualStrength Sample Strength Strength Indices Factors No. (MPa) (MPa) I₁₀I₃₀ I₆₀ R_(10,30) R_(30,60) F15A 6.31 6.31 N.A. 8.1 18.4 N.A. 34.3 F15B6.22 6.22 N.A. 8.5 18.9 N.A. 34.7 F15C 5.65 5.65 N.A. 18.5 35.5 N.A.56.7 Avg. 6.06 6.06 N.A. 11.7 24.3 N.A. 41.9 N.A. = not available due tolarge initial deformations after first-crack

TECHNICAL REPORT No. 6d SUBJECT: Japanese Toughness Parameters andToughness Performance Levels Fiber Type: Hybrid Synthetic Fibers FiberAddition Rate: 1.5% by vol. Japanese Toughness Parameters First-CrackUltimate Toughness Toughness Sample Strength Strength Toughness FactorPerformance No. (MPa) (MPa) (kN · mm) (MPa) Levels F15A 6.31 6.31 12.71.99 III F15B 6.22 6.22 13.1 2.00 III F15C 5.65 5.65 22.3 3.33 IV Avg.6.06 6.06 16.0 2.44 III

TECHNICAL REPORT No. 6e SUBJECT: ASTM C1018 Toughness Parameters andResidual Strength Factors Fiber Type: Hybrid Synthetic Fibers FiberAddition Rate: 1.9% by vol. Residual First-Crack Ultimate StrengthSample Strength Strength Toughness Indices Factors No. (MPa) (MPa) I₁₀I₃₀ I₆₀ R_(10,30) R_(30,60) F20A 6.22 6.22 N.A. 18.1 34.0 N.A. 53.0 F20B6.14 6.14 8.4 20.7 41.4 61.5 69.0 F20C 6.02 6.02 7.5 21.3 42.5 69.0 70.7Avg. 6.13 6.13 N.A. 20.0 39.3 N.A. 64.2 N.A. = not available due tolarge initial deformations after first-crack

TECHNICAL REPORT No. 6f SUBJECT: Japanese Toughness Parameters andToughness Performance Levels Fiber Type: Hybrid Synthetic Fibers FiberAddition Rate: 1.9% by vol. Japanese Toughness Parameters First-CrackUltimate Toughness Toughness Sample Strength Strength Toughness FactorPerformance No. (MPa) (MPa) (kN · mm) (MPa) Levels F20A 6.22 6.22 22.03.45 IV F20B 6.14 6.14 25.8 3.90 IV F20C 6.02 6.02 29.7 4.63 V Avg. 6.136.13 25.9 3.99 IV

TECHNICAL REPORT No. 7 SUBJECT: Australian Round Panel Test ResultsAustralian Round Panel Test Fiber Addition In situ Rate Fiber Peak_(—)Energy Mix % by Content Load Nm = J Number vol. kg/m³ % by vol. kN 0–10mm 0–20 mm 0–30 mm 0–40 mm F10 1.0 9.1 0.94 32.2 163 309 428 525 F15 1.513.7 1.18 29.8 185 368 515 641 F20 1.9 17.3 1.58 27.9 226 445 611 747

Example 3

The performance characteristics, strength and toughness, of concretemixtures reinforced with the fibers of the present invention wereanalyzed. A number of three-dimensionally reinforced concrete specimens(beams and cylinders) using four fiber dosages (0.5, 1.0, 1.5, 2.0percent by volume) had been cast and tested to evaluate the strength andtoughness characteristics. The strength tests included the compressivestrength, flexural strength (modulus of rupture), first crack strength,and impact strength. The toughness properties evaluated were modulus ofelasticity. The toughness indexes I5, I10, I20, I30 and residualstrengths were calculated according to the ASTM C 1018 test procedure,and the flexural toughness factor (JCI) and the equivalent flexuralstrength were calculated according to the Japanese Society of CivilEngineers standard specifications. A new test method (ASTM C1399-98) wasalso used to determine the average residual strength of the concretemixtures reinforced with the four different dosages of the present fiberinvention.

A total of four mixes, one for each fiber content were made. The basicmixture proportions were the same for all four concrete mixtures, exceptfor two mixes with 1.5 and 2.0 percent by fiber volume, the workabilitywas increased by increasing water cement ratio. The fiber reinforcedconcrete mixtures were mixed, placed, consolidated, finished and curedunder identical conditions. The test results indicate that there was noballing or segregation due to the addition of fibers at the recommendeddosages for all four mixes.

Test results show that there was a significant increase in the flexuralstrength and a slight increase in the first crack strength as the fibercontent was increased from 0.5 to 2.0 percent by volume. The ASTMtoughness indexes and the Japanese toughness factors and equivalentflexural strengths were also significantly increased as the fibercontent increased. There was also a significant increase in impactstrength for an increase in fiber content.

Test results further show that very high average residual strengths(ARS) (ASTM C1399) were obtained and the ARS values increased as thefiber content increased. The ARS values were 234 psi (16.45 kg/cm²), 451psi (31.71 kg/cm²), 454 psi (31.92 kg/cm²), and 654 psi (45.98 kg/cm²)for fiber contents of 0.5, 1.0, 1.5, 2.0 percent by volume,respectively.

Overall, the performance of reinforced concrete incorporating the fibersof the present invention were similar and/or better than the concretesreinforced with the best steel fibers available in the market comparedon an equal weight or cost basis. The following performance relatedtests were performed to determine the physical characteristic of thefibers of the present invention: 1) the properties of fresh concreteswith different dosages of fibers; 2) the properties of hardenedconcretes such as compressive strength, static modulus, static flexurestrength, and unit weight; 3) the toughness indices by the ASTM methodwith the help of load deflection curves; 4) comparisons in the loaddeflection curves for the four fiber reinforced concretes; 5)comparisons in the toughness factor and equivalent flexural strengthcalculated according to the Japanese Society of Civil Engineersspecifications; and 6) evaluation in the average residual strength (ARS)according to ASTM C 1399 test procedure for the specimens made from allfour mixes.

Materials

Hybrid fibers as described herein were used and tested in thisexperiment. Type I/II Normal Portland cement satisfying ASTM C 150requirements was used. The cement was supplied by Dakotah Cement, SouthDakota. The coarse aggregate used was crushed limestone, obtained from alocal source in Rapid City, S. Dak. The maximum size of the aggregateused was 19 mm (¾″) with absorption of 0.45%. The fine aggregate usedwas natural sand with a water absorption coefficient of 1.6%. Both thecoarse and fine aggregates were according to the grading requirements ofASTM C33. The water used was tap water from the Rapid City Municipalwater supply system.

Mixes

A total of 4 mixes were prepared. The dosages of fibers added to theconcrete were in amounts of 0.5, 1.0, 1.5 and 2.0 percent by volume ofconcrete. The water cement ratio was kept constant at 0.5 for two mixeswith 0.5 and 1.0 percent by volume of fiber and it was increased to 0.55for concrete with higher dosages of fibers (1.5 and 2.0 percent byvolume). The mix proportions and designations are given in Table 4,below.

Mixing Procedure

All mixing was performed in a nine cubic feet capacity mixer. The fiberswere weighed accurately and kept in a separate plastic container. Firstthe buffer mix was prepared. Next, coarse aggregates were introducedinto the mixer. Thereafter, sand and two thirds of the water were addedand mixed for one minute. Cement was then added along with the remainingone third of the water. The fibers of the present invention were addedand the ingredients were mixed for three minutes. Following a threeminute rest period, the mixture underwent a final mixing stage for 2minutes to completely distribute the fibers.

Test Specimens

The following specimens were cast from each mix: 1) four 101×101×356 mm(4in×4in×14in) beams for ASTM toughness test; 2) four 101×101×356 mm (4in×4 in×14 in) beams for ARS Test (ASTM C 1399); 3) three 152×304 mm (6in×12 in) cylinders for compressive strength and static modulus; and 4)ten 152×63 mm (6 in×2.5 in.) cylinders for impact test. The specimenswere cast according to the ASTM standards and covered with plasticsheets for 24 hours at room temperature. The specimens were then placedin a lime saturated water tank maintained at 22.22° C. (72° F.), andremained in water till they were tested for 14-day strengths.

Tests for Fresh Concrete

Freshly mixed concrete was tested for slump (ASTM C143), air content(ASTM C231), fresh concrete unit weight (ASTM C 138), and concretetemperature. No balling or segregation was observed due to the additionof fibers.

Tests for Hardened Concrete

1. Static Modulus and Compressive Strength

Cylinders were tested for static modulus (ASTM C469) and compressivestrength (ASTM C39) at 28 days.

2. Static Flexure Test

Beams were tested at 28 days for the static flexural strength (ASTM C1018). The span length was 12 inches (30.5 cm). This test is adeflection-controlled test. The rate of deflection was kept in the rangeof 0.002 to 0.004 inches per minute (0.005 to 0.010 centimeter perminute) as per ASTM C 1018. The load at first crack and the maximum loadreached were noted for every beam. From the load and deflectionsobtained, load-deflection curves were drawn from which the toughnessindices and the residual strength factors by ASTM method werecalculated.

The deflection measurements were performed using test apparatusaccording to ASTM standards. A specially designed frame was used tomount the dial gauge. This frame was supported only at the four points,which was on the neutral axis above the supports. The dial gauge wasfixed such that it was touching the center point of the bottom surface.This arrangement allowed for the measure of the true deflectionexcluding any extraneous deformations due to crushing of concrete atsupports and load points, and any deformations and strains induced inthe testing frame. Because the deflection is measured at the centerpoint, any slight warping or twisting of beam will not affect truedeflections measured. Hence the deflections measured were the truedeflections of the beam.

3. Load Deflection Behavior

The area under the curve represents the energy absorbed by the beam.Load deflection curves for both the pre first crack and post first crackdata, were drawn. Toughness indices and the residual strength indices'were calculated by using these curves.

4. Flexural Toughness (Energy Absorption)

Toughness, or energy absorption, of concrete is increased considerablyby the addition of fibers. Toughness index is the measure of the amountof energy required to deflect the 100 mm (4 in) beam in the modulus ofrupture test. The most important variable governing the toughness indexof fiber reinforced concrete is the fiber efficiency. Other parametersinfluencing the toughness index are the position of the crack, the fibertype, aspect ratio, volume fraction and the distribution of fibers.Fiber efficiency is controlled by the resistance of the fiber to pullout from the matrix, which is developed as a result of the bond strengthat the fiber matrix interface. The advantage of pullout type of failureof fiber is that, it is gradual and ductile, compared to a more rapidand catastrophic failure, which may occur, if fibers are brittle andfail in tension with little or no elongation. The fiber pullout orfracture depends on the yield strength of the fibers, the bond andanchorage between the matrix and the fiber.

Toughness index (ASTM C1018) is a dimensionless parameter, which definesor finger prints the shape of the load deflection curve. Indices havebeen defined on the basis of three service levels, identified as themultiples of the first crack deflection. The index is computed bydividing the total area under the load deflection curve up to the firstcrack deflection. The toughness index I5 is calculated at three timesthe first crack deflection. Likewise I10, I20 and I30 are the indices upto 5.5, 10.5 and 15.5 times the first crack deflection respectively.

5. Average Residual Strength Test

The rate of platen or crosshead movement was set at 0.65+/−0.15 mm/min(0.025+/−0.005 in/min), using the mechanical dial gauge when necessary,before the specimen was loaded. The sample beam was turned on its sidewith respect to its position as molded and placed on top of the steelplate to be loaded with the specimen. The plate and the beam were placedon the support apparatus so that the steel plate was centered on thelower bearing blocks and the concrete beam was centered on the steelplate. The displacement transducers were adjusted according to thechosen apparatus for obtaining net deflection. Mega-Dac data acquisitionsystem was used in the test. (Note: The purpose of the stainless steelplate is to support the test beam during the initial loading cycle andhelp control the expected high rate of deflection of the specimen uponcracking. A center hole was placed in the steel plate to accommodateplacing a displacement transducer probe directly against the bottom ofthe test sample.)

A data acquisition system was activated and it was responded to signalsfrom all load and displacement transducers. Thereafter, the specimen andsteel plate combination were loaded at the set rate and the loading wascontinued until the specimen cracked or it reached a deflection of 0.50mm (0.02 in), whichever occurred first. If cracking had not occurred atthis stage, the test is considered invalid. The maximum load tocalculate modulus of rupture was not used in accordance with Test MethodC 78 as this load includes load carried by the steel plate as well as bythe concrete specimen.

In anticipation of reloading the cracked beam specimen only, the steelplate was removed and the cracked beam was centered on the lower bearingblocks retaining the same orientation as during the initial loading testcycle. The displacement transducers were adjusted to lightly contact thebeam sample in accordance with the chosen method for obtaining netdeflection so that readings were immediately obtained upon beamreloading. The deflection-recording device was again brought to zero andreloaded at the specified rate. The test was terminated at a deflectionof 1.25 mm (0.50 in) as measured from the beginning of reloading.

Using the Excel package the graphs were drawn and the residual strengthswere calculated by the formulas given below.

Test Apparatus and Set-Up

The test apparatus satisfied the ASTM standards. A specially designedframe was used to mount the dial gauge with 0.0025-mm (0.0001-in.)resolution. This frame was supported only at the four points, which areon the neutral axis above the supports. The dial gauge was fixed suchthat it was touching the center point of the bottom surface. Thisarrangement enabled the measurement of the true deflection excluding anyextraneous deformations due to crushing of concrete at supports and loadpoints and any deformations and strains induced in the testing frame.Because the deflection is measured at the center point, any slightwarping or twisting of beam will not affect true deflections measured.In addition to the dial gage, LVDT was also mounted and the deflectionswere recorded by a data acquisition system. These readings were used forverification of dial gage readings.

Calculations

The average residual strength for loads at reloading deflections of0.50, 0.75, 1.00, and 1.25 mm (0.02, 0.03, 0.04, and 0.05 in) arecalculated using the following formula:ARS=((P _(A) +P _(B) +P _(C) +P _(D))/4)×KwhereK=1/bd ², mm⁺²((in⁻²)andARS=Average Residual strength, Mpa (psi)P _(A) +P _(B) +P _(C) +P _(D)=recorded loads at specified deflections,N (lbf)1=span length, mm (in),b=average width of specimen, mm (in) andd=average depth of specimen, mm (in)Impact Test

The specimens were tested for impact strength at an age of 14 days bythe drop weight test method (ACI Committee 544). In this method, theequipment consisted of a standard manually operated 4.54 kg (10 lbs)weight with a 457 mm (18 inch) drop (compactor), a 63.5 mm (2-½ inch)diameter hardened steel ball, a flat steel base plate with a positioningbracket and four positioning lugs. The specimen was placed on the baseplate with its rough surface facing upwards. The hard steel ball wasplaced on the top of the specimen and within the four positioningbrackets. The compactor was placed with its base on the steel ball. Thetest was performed on a flat rigid surface to minimize the energylosses. The hammer was dropped consecutively, and the number of blowsrequired to cause the first visible crack on the specimens was recorded.The impact resistance of the specimen to ultimate failure was alsorecorded by the number of blows required to open the crack sufficientlyso that the pieces of specimen were touching at least three of the fourpositioning lugs on the base plate.

Test Results

1. Fresh Concrete Properties

Room temperature, humidity and concrete temperature were recorded toensure that all the mixes were carried out under similar conditions. Theroom temperature and humidity varied in the range of 65° F. to 85° F.and 35% to 45% respectively. The concrete temperature varied from 65 to73° F. (18.3–22.8° C.). The unit weights of higher dosage fiber concretewere slightly less than the concretes with lower fiber dosages. Thefresh concrete properties are given in Table 5.

2. Workability

The test results indicate that satisfactory workability can bemaintained even with the addition of the fibers. The concrete started toharden in about 40 to 45 minutes. The fibers mixed well and wereuniformly distributed throughout the concrete. Overall, there was nobridging, bleeding or segregation. Even though the slump values show thedecreasing trend with the addition of the fibers, no difficulty wasencountered in placing and consolidating the concrete with the use ofthe table vibrator.

3. Air Content

The air content ranged from 1.4 to 1.8%. No air-entraining agent wasused. Therefore the measured air is considered as entrapped air.

Hardened Concrete Properties

1. Compressive Strength & Static Modulus Test

The results of the compressive strength test are tabulated in Table 6and show that there is a variation in the compressive strength.Compressive strength depends on water cement ratio and air content. Ifthe water cement ratio is less, compressive strength will be more.Likewise, if the air content is more, the compressive strength will beless.

The average compressive strengths for mixes E1 and E2 with 0.50 w/cratios were psi (349 kg/cm²) and 4760 psi (335 kg/cm²), respectively.This slight variation is within the normal variation expected inconcrete testing. The average compressive strength for mixes E3 and E4with 0.55 w/c ratios were 3570 psi (251 kg/cm²) and 3860 psi (271kg/cm²) respectively.

Because the concrete compressive strengths varied, a normalizationprocedure was used in order to compare the flexural strength, firstcrack strength, and first crack toughness for all concrete mixtures onan equal compressive strength basis. The comparison was made on thecompressive strength of mix El, which is 4960 psi (349 kg/cm²). It waswell-established in literature and codes that the flexural strength ofconcrete varies proportionally to the square root of the compressivestrength of concrete (ACI code 318). Therefore, for the calculation ofnormalized flexural strength, the following equation was used.

$f_{r} = \frac{f_{ra}\sqrt{4960}}{\sqrt{f_{c}^{\prime}}}$where f_(ra) is the actually measured flexural strength and f_(c)′ isthe compressive strength of that concrete. The values given in Tables 7to 9 are normalized values.

A ductile mode of failure, as compared to plain concrete's brittlefailure, was observed while testing for compressive strength. The fiberreinforced concrete cylinders continued to sustain the load andunderwent deformation without totally breaking into pieces. The changeof mode of failure from a brittle type to a ductile type is an importantcontribution due to the addition of fibers.

The static modulus test served primarily as a means of quality control.The results indicate that the mixes were reasonably consistent and theaddition of fibers had no effect on the static modulus. The staticmodulus values are given in Table 6.

2. Static Flexural Strength (Modulus of Rupture)

The static flexural strength test results, the first crack load,ultimate load and flexural stress are given in Table 7. When the fiberconcrete beams were loaded in flexure, the behavior was approximatelylinear up to the first crack and then the curve was significantlynon-linear and reached its peak at the ultimate strength, or at themaximum sustained load. In contrast, the control (plain) concrete beamswould fail immediately at the appearance of the first crack and hencethe first crack strength and flexural strength (modulus of rupture)would be the same for control concrete. The factors that significantlyinfluence the flexural strength and the toughness are the fiber type andthe fiber volume. The first crack strength variation versus fibercontent is shown in FIG. 7. As illustrated, there is an increase in thefirst crack strength as the fiber content increased from 0.5 to 2.0percent. The modulus of rupture (static flexural strength) versus fibercontent is shown in FIG. 8. As illustrated, there is a significantincrease in the flexural strengths for 1.5 and 2.0 percent fibercontents. The average flexural strength for mixes E1 and E2 were 643 psi(45 kg/cm²) and 658 psi (46 kg/cm²) respectively whereas for mixes E3and E4, the strengths were 720 psi (51 kg/cm²) and 731 psi (51kg/cm²)respectively which is a 13.7 percent increase.

3. ASTM Toughness Indexes and Residual Strengths

The calculated ASTM toughness indexes and residual strengths are givenin Table 8. The first crack toughness versus fiber content is shown inFIG. 9 and the ASTM toughness indexes I5, I10, I20, and I30 are shown inFIG. 10. The test results show that when the fibers of the presentinvention are added to the concrete there is an increase in thetoughness and ductility of the concrete. Moreover, the test results showthat higher fiber content produces a higher toughness and ductility.

4. Japanese Standard Method of Calculating Flexural Toughness Factor andEquivalent Flexural Strength

In addition to the ASTM C-1018 toughness indexes, the equivalentflexural strength and the flexural toughness, as specified by theJapanese Society of Civil Engineers (JSCE) were calculated for all thespecimens and are given in Table 9. The variation of the Japanesetoughness and the equivalent flexural strength with an increase in fibercontent from 0.5 to 2.0 percent by volume are shown in FIGS. 11 and 12,respectively. The results show that there is a very clear indicationthat the toughness and equivalent flexural strength increases with anincrease in fiber content and this increase is approximately linear withthe increase in fiber content. The toughness increased from 108 in-lbs(1.24 kg-m) to 304 in-lbs (3.5 kg-m) as the fiber content increased from0.5 to 2.0 percent. The equivalent flexural strength increased from 244psi (17.2 kg/cm²) to 679 psi (47.7 kg/cm²) with an increase in fibercontent from 0.5 to 2.0 percent.

5. Impact Strength

The drop weight (ACI Committee 544) impact test results are given inTable 10. The number of blows to first crack and final failure versusthe fiber content are shown in FIG. 14. Though a relatively simple test,if more specimens are tested, the mean values indicate qualitatively agood index of the impact resistance of the material. Ten specimens weretested for each concrete and the average values are plotted in FIG. 14.The impact resistance increased considerably with an increase in fibercontent. It is well known from previous testing that the plain concreteimpact resistance will be about ⅙ to 1/15 of that fiber concrete with0.25 to 2.0 percent by volume.

6. Average Residual Strength

Four beams were tested for fiber content. The average widths and depthsof the beams, the loads obtained upon reloading at deflections of 0.5,0.75, 1.0, and 1.25 mm (0.020, 0.030, 0.040, 0.050 inch), and theaverage residual strengths (ARS) are given in Table 11. Theload-deflection curves obtained by reloading and re-testing thepre-cracked beam (without the steel plate) are given in FIGS. 15–26. Thecalculated ARS values for all four fiber reinforced concretes are shownin FIG. 7. The test results indicate that the average residual strengthincreased considerably with an increase in fiber content. The ARS valueswere 234 psi (16.5 kg/cm²), 451 psi (31.7 kg/cm²), 454 psi (31.9kg/cm²), and 654 psi (46.0 kg/cm²) for fiber contents of 0.5, 1.0, 1.5,2.0 percent by volume, respectively. It can be seen that 180 percentincrease in ARS was obtained when the fiber content was increased from0.5 to 2.0 percent by volume.

Since the ARS values are only due to the influence of fiber,irrespective of the compressive strength of the concrete, the ARS valueswere not normalized. The mixes E1 (with 0.5 percent fiber) and E2 (with1.0 percent fiber) had compressive strengths of 4960 psi and 4760 psi,respectively, whereas the mixes E3 (with 1.5 percent fiber) and E4 (with2.0 percent fiber) had lower compressive strengths, 3570 psi (251kg/cm²) and 3860 psi (271 kg/cm²), respectively. Despite these lowercompressive strengths, a substantial increase in the ARS values wasobserved.

Conclusions

The test results discussed above lead to the following conclusions andobservations. First, the hybrid fibers of the present invention may beincorporated in concrete up to 2.0 percent by volume without causing anyballing, clogging, and segregation. In addition, satisfactoryworkability was maintained with the addition of four fiber contents atthe dosages of 0.5, 1.0, 1.5, and 2.0 percent by volume. Compared toplain concrete, there was a considerable increase in the first crackstrength, flexural strength and both ASTM and Japanese toughness values.The first crack strength increased with higher fiber content. Moreover,there was a substantial increase in the impact resistance when thefibers of the present invention are incorporated into concrete whencompared to plain concrete. The impact resistance increased withincreasing fiber content. Significantly, the impact resistance achievedthrough the use of the fibers of the present invention was the same orhigher than that of the best steel fiber reinforced concrete with thefiber content by volume percentage. In addition, for all fiberreinforced concrete mixtures employing the fiber of the presentinvention, the mode of failure was changed from a brittle to a ductilefailure when subjected to compression or bending. This ductilityincreased with increasing fiber content. Furthermore, the averageresidual strengths (ARS) of concrete incorporating the fiber of thepresent invention, calculated according to the ASTM C 1399 testprocedure, was extremely high, which indicated that the fiber was veryeffective in sustaining the post crack load. The ARS value increasedwith increases in fiber content. There was an 180 percent increase inthe ARS value when the fiber content was increased from 0.5 to 2.0percent by volume. This increase took place despite a reduction incompressive strength from 4960 psi (349 kg/cm²) to 3860 psi (271kg/cm²). Accordingly, the performance of fiber reinforced concretemixtures of the present invention were similar or superior than theconcrete reinforced with the best steel fibers available in the marketcompared on an equal weight or cost basis.

TABLE 4 Mix Proportions Weight in kg(lbs) Water Coarse Fine Mix CementFibers Cement Agg. Agg Water Design. Ratio kg(lbs) Vol % kg(lbs) kg(lbs)kg(lbs) kg(lbs) E1 0.5 0.318 (0.7) 0.5 25.22 (55.6) 64.86 (143) 64.86(143) 12.61 (27.80) E2 0.5 0.635 (1.4) 1.0 25.22 (55.6) 64.86 (143)64.86 (143) 12.61 (27.80) E3 0.55 0.953 (2.1) 1.5 25.22 (55.6) 64.86(143) 64.86 (143) 13.88 (30.6) E4 0.55  1.27 (2.8) 2.0 25.22 (55.6)64.86 (143) 64.86 (143) 13.88 (30.6)

TABLE 5 Properties of Fresh Concrete Room Concrete. Unit Initial MixTemp Temp. Weight Slump Air Desig- ° F. Room ° F. lb/ft³ in Contentnation (° C.) Humidity (° C.) (kg/m³) (cm) (%) E1 65 45 64.8 147.6 1.251.8 (18) (18.2) (2364.5) (3.18) E2 85 35 69.1 146   0.75 1.8 (29) (20.6)(2338.9) (1.91) E3 80 45 70.9 145.2 0.40 1.4 (27) (21.6) (2326.1) (1.02)E4 85 40 73.2 145.2 0.25 1.4 (29) (22.9) (2326.1) (0.64) SI UnitConversion 1 in = 2.54 cm ° F. = 5/9 (° F. − 32)° C. ft³ = 0.02832 m³lb/ft³ = 16.02 kg/m³

TABLE 6 Cylinder Compressive Strength and Static Modulus Diameter LengthUnit weight Static modulus Comp. strength Specimen Age in. in. lb/ft³10⁶ psi psi ID (Days) (cm) (cm) (kg/m³) (kg/cm²) (kg/cm²) E1-1 14 5.99512.042 149 3.90 5225 (15.227) (30.587) (2387) (0.274) (367) E1-2 146.025 11.958 150 3.86 4770 (15.304) (30.373) (2403) (0.271) (335) E1-314 6.001 12.083 151 3.89 4880 (15.243) (30.691) (2419) (0.273) (343)Average 150 3.88 4960 (2403) (0.272) (349) Std. Dev  1.00 0.02  237 %C.V  0.67 0.54   4.79 E2-1 14 6.078 12.083 146 3.79 4640 (15.438)(30.691) (2339) (0.267) (326) E2-2 14 5.989 12.167 150 3.90 4950(15.212) (30.904) (2403) (0.274) (348) E2-3 14 6.000 12.083 149 3.894685 (15.240) (30.691) (2387) (0.273) (329) Average 148 3.86 4760 (2371)(0.271) (335) Std. Dev  2.08 0.06  168 % C.V  1.40 1.58   3.52 E3-1 146.012 12.167 147 3.87 3435 (15.271) (30.904) (2355) (0.272) (242) E3-214 6.000 12.000 148 3.89 3820 (15.240) (30.480) (2371) (0.273) (269)E3-3 14 5.967 12.083 149 3.28 3450 (15.156) (30.691) (2387) (0.231)(243) Average 148 3.68 3570 (2371) (0.259) (251) Std. Dev  1.00 0.35 218 % C.V  0.68 9.42   6.11 E4-1 14 5.973 12.083 147 3.27 3785 (15.171)(30.691) (2355) (0.230) (266) E4-2 14 6.006 12.042 147 3.24 3850(15.255) (30.587) (2355) (0.228) (271) E4-3 14 5.991 12.083 146 3.253940 (15.171) (30.691) (2339) (0.229) (277) Average 147 3.25 3860 (2355)(0.229) (271) Std. Dev  0.58 0.02  78 % C.V  0.39 0.47   2.02 SI UnitConversion Factors 1 inch = 2.54 cm 1 psi = 703 kg/m² 1 lb = 0.4536 kglb/ft³ = 16.02 kg/m³

TABLE 7 FIRST CRACK STRENGTH AND MAXIMUM FLEXURAL STRENGTH 14 DAYS Maxi-First Crack mum Flexural Load Stress Load Strength Mixture Specimen Agelbs psi lbs psi Type # (Days) (kg) (kg/cm²) (kg) (kg/cm²) E1 E1-1 143500 623 3600 641 (1588) (44) (1633) (45) E1-2 14 3000 527 3598 632(1361) (37) (1632) (44) E1-3 14 3000 545 3522 640 (1361) (38) (1598)(45) E1-4 14 3000 509 3885 659 (1361) (36) (1762) (46) Average 551 643(39) (45) E2 E2-1 14 3062 589 3267 628 (1389) (41) (1482) (44) E2-2 143573 612 3840 658 (1621) (43) (1742) (46) E2-3 14 3573 629 3915 689(1621) (44) (1776) (48) E2-4 14 3573 648 3628 658 (1621) (46) (1646)(46) Average 619 658 (44) (46) E3 E3-1 14 2947 504 3438 588 (1790) (35)(1560) (41) E3-2 14 3536 626 4078 722 (1604) (44) (1850) (51) E3-3 144125 677 4427 726 (1871) (48) (2008) (51) E3-4 14 4715 804 4938 842(2139) (57) (2240) (59) Average 653 720 (46) (51) E4 E4-1 14 3967 6794203 719 (1799) (48) (1907) (51) E4-2 14 3401 593 3838 670 (1543) (42)(1741) (47) E4-3 14 3967 698 4529 797 (1799) (49) (2054) (56) E4-4 143967 703 4178 740 (1799) (49) (1895) (52) Average 668 731 (47) (51) SIUnit Conversion Factors 1 inch = 25.4 mm 1 lb = 0.4536 kg 1 psi = 703kg/m²

TABLE 8 ASTM - TOUGHNESS INDICES - 14 DAYS First Crack ResidualToughness Toughness Strength Mixture inch-lbs Toughness Ratios IndicesType Specimen # (Nm) I5 I10 I20 I30 I10/I5 I20/I10 I30/I20 R_(5,10)R_(10,20) E1 E1-1 0.8 (0.09) 3.66 6.83 12.67 17.84 1.9 1.9 1.4 63.4 58.4E1-2 1.0 (0.11) 3.29 6.07 11.10 15.45 1.8 1.8 1.4 55.6 50.3 E1-3 1.3(0.15) 4.57 8.67 15.68 21.11 1.9 1.8 1.3 82.0 70.1 E1-4 1.0 (0.11) 4.367.89 12.75 16.77 1.8 1.6 1.3 70.6 48.6 Average 1.0 (0.11) 3.97 7.3713.05 17.79 1.9 1.8 1.4 67.9 56.9 E2 E2-1 0.9 (0.10) 3.4 6.0 10.8 16.01.7 1.8 1.5 50.6 48.7 E2-2 1.5 (0.17) 3.8 6.8 11.4 15.7 1.8 1.7 1.4 61.045.8 E2-3 0.9 (0.10) 3.3 6.0 10.3 13.5 1.8 1.7 1.3 52.8 43.1 E2-4 0.9(0.10) 3.3 6.0 10.6 14.1 1.8 1.8 1.3 53.8 45.6 Average 1.0 (0.11) 3.56.2 10.8 14.8 1.8 1.7 1.4 54.6 45.8 E3 E3-1 0.7 (0.08) 3.7 7.1 14.1 21.41.9 2.0 1.5 68.0 70.2 E3-2 0.7 (0.08) 4.0 7.6 14.6 21.2 1.9 1.9 1.5 72.469.5 E3-3 0.8 (0.09) 4.1 7.8 15.2 21.7 1.9 1.9 1.4 75.6 74.0 E3-4 2.1(0.24) 4.3 7.8 14.8 22.3 1.8 1.9 1.5 71.8 69.7 Average 1.1 (0.12) 4.07.6 14.7 21.6 1.9 1.9 1.5 72.0 70.9 E4 E4-1 1.2 (0.14) 3.6 6.6 11.8 17.11.8 1.8 1.4 59.6 52.3 E4-2 1.1 (0.12) 4.2 7.9 14.7 20.4 1.9 1.9 1.4 75.067.6 E4-3 2.6 (0.29) 3.4 6.4 12.5 18.5 1.9 1.9 1.5 60.2 60.5 E4-4 1.3(0.15) 4.7 9.3 18.4 27.1 2.0 2.0 1.5 91.8 90.6 Average 1.5 (0.17) 4.07.6 14.3 20.8 1.9 1.9 1.5 71.7 67.8 Conversion Factor: 1 in-lb = 0.113Nm

TABLE 9 JAPANESE STANDARD - TOUGHNESS & EQUIVALENT FLEXURAL STRENGTH -14 DAYS Toughness Equivalent Flexural Mixture Specimen Age inch-lbsStrength psi Type # (Days) (Nm) (kg/cm²) E1 E1-1 14.0  93.5 (10.6) 219(15.4) E1-2 14.0 101.1 (11.4) 226 (15.8) E1-3 14.0  99.7 (11.3) 226(15.8) E1-4 14.0 137.5 (15.6) 304 (21.4) Average 107.9 (12.2) 244 (17.2)E2 E2-1 14.0 177.2 (20.0) 428 (30.1) E2-2 14.0 202.1 (22.9) 434 (30.5)E2-3 14.0 154.6 (17.5) 343 (24.1) E2-4 14.0 164.3 (18.6) 377 (26.5)Average 174.6 (19.7) 395 (27.8) E3 E3-1 14.0 250.3 (28.3) 542 (38.1)E3-2 14.0 240.1 (27.2) 523 (36.8) E3-3 14.0 320.7 (36.3) 657 (46.2) E3-414.0 368.6 (41.7) 776 (54.6) Average 294.9 (33.4) 624 (43.9) E4 E4-114.0 290.2 (32.8) 642 (45.1) E4-2 14.0 213.9* (24.2) 482* (33.9) E4-314.0 331.5 (37.5) 744 (52.3) E4-4 14.0 290.5 (32.9) 651 (45.8) Average304.1 (34.4) 679 (47.7) *Omitted as outlier Conversion Factors: 1 psi =703 kg/m² 1 in-lb = 0.113 Nm

TABLE 10 IMPACT TEST RESULTS - 14 DAYS Number of Blows to Difference inno. Mixture Age Specimen First of blows from Type (Days) # Crack Failurefirst crack to failure E1 14 E1-1 48 201 153 14 E1-2 106 192 86 14 E1-3177 246 69 14 E1-4 189 270 81 14 E1-5 20 112 92 14 E1-6 107 211 104 14E1-7 23 127 104 14 E1-8 58 195 137 14 E1-9 51 186 135 14 E1-10 62 193131 Average 84 193 109 E2 14 E2-1 54 289 235 14 E2-2 58 337 279 14 E2-395 410 315 14 E2-4 110 405 295 14 E2-5 99 442 343 14 E2-6 105 433 328 14E2-7 110 428 318 14 E2-8 130 413 283 14 E2-9 113 429 316 14 E2-10 115450 335 Average 99 404 305 E3 14 E3-1 43 192 149 14 E3-2 125 374 249 14E3-3 84 282 198 14 E3-4 123 632 509 14 E3-5 110 370 260 14 E3-6 58 210152 14 E3-7 115 390 275 14 E3-8 105 350 245 14 E3-9 95 380 285 14 E3-1080 330 250 Average 94 351 257 E4 14 E4-1 210 484 274 14 E4-2 190 460 27014 E4-3 170 425 255 14 E4-4 260 495 235 14 E4-5 288 505 217 14 E4-6 240489 249 14 E4-7 180 435 255 14 E4-8 205 455 250 14 E4-9 236 482 246 14E4-10 185 410 225 Average 216 464 248

TABLE 11 AVERAGE RESIDUAL STRENGTH (ARS) Load in lbs (kg) at DeflectionARS Mixture Age 0.02 in 0.03 in 0.04 in 0.05 in Breadth Depth psi Type(Days) Specimen # (0.05 cm) (0.08 cm) (0.10 cm) (0.13 cm) in (cm) in(cm) (kg/m²) E1 14 E1-5 — — — — — — — 14 E1-6 1002 (455)  997 (453)  975(442)  921 (418) 4.225 (10.732) 4.098 (10.409) 165 (0.24) 14 E1-7 1502(682) 1558 (707) 1592 (722) 1592 (722) 4.175 (10.605) 4.055 (10.300) 273(0.39) 14 E1-8 1521 (690) 1525 (692) 1510 (685) 1472 (668) 4.167(10.584) 4.056 (10.302) 264 (0.38) Average 234 (0.33) E2 14 E2-5 2522(1144) 2617 (1187) 2598(1178) 2507 (1137) 4.238 (10.765) 4.043 (10.269)444 14 E2-6 2637 (1197) 2707 (1228) 2685 (1218) 2650 (1202) 4.201(10.671) 4.031 (10.239) 469 (0.68) 14 E2-7 3322 (1507) 3490 (1583) 3522(1598) 3496 (1586) 4.353 (11.057) 4.130 (10.490) 559 (0.80) 14 E2-8 2012(92) 2044 (927) 2059 (934) 1992 (904) 4.282 (10.876) 4.142 (10.521) 331(0.47) Average 451 (0.64) E3 14 E3-5 1868 (848) 1929 (875) 1969 (893)1979 (898) 4.292 (10.902) 3.881 (9.858) 359 (0.51) 14 E3-6 2781 (1262)2958 (1342) 3147 (1427) 3238 (1469) 4.196 (10.658) 3.959 (10.056) 553(0.79) 14 E3-7 2435 (1105) 2399 (1088) 2428 (1101) 2412 (1094) 4.204(10.678) 4.008 (10.180) 430 (0.61) 14 E3-8 2485 (1128) 2601 (1180) 2764(1254) 2827 (1282) 4.233 (10.752) 3.996 (10.150) 474 (0.67) Average 454(0.65) E4 14 E4-5 2817 (1278) 3249 (1474) 3356 (1522) 3377 (1532) 4.293(10.904) 4.161 (10.569) 517(0.74) 14 E4-6 4215 (1912) 4709 (2136) 4790(2173) 4734 (2147) 4.333 (11.006) 4.082 (10.368) 767 (1.09) 14 E4-7 4225(1917) 4818 (2185) 4904 (2224) 4905 (2225) 4.312 (10.953) 4.086 (10.378)786 (1.12) 14 E4-8 3398 (1542) 2999 (1360) 3253 (1476) 3247 (1473) 4.287(10.889) 4.064 (10.323) 546 (0.78) Average 654 (0.93) SI Unit ConversionFactors 1 inch = 25.4 mm 1 lb = 0.4536 kg 1 psi = 703 kg/m²

As set forth above, it is contemplated that embodiments of the fibercomposition of the present invention provide improved properties tovarious types of cementitious material, including asphalt-basedmaterial. For example, embodiments of the present invention wereemployed in test strips of asphalt roadways in amounts of about 2.0 toabout 3.3 pounds per ton along with an oil emulsion and aggregate (⅜″ (1cm) limestone chip) and monitored for surface failures and damageresulting from typical environmental wear and use. The test strips werefull width (edge of pavement to edge of pavement). Cold-mix asphaltroadways that did not employ the fiber compositions of the presentinvention had experienced surface failure, such as unraveling on hills,curves, and shaded areas of recently paved roads. Surface failures weredue to longitudinal and transverse separation attributed to heave axleloads, such as, truck and farming equipment traffic. Road maintenancevehicles, such as snow plows, and their method of snow removalaccentuated the surface failures. Test results indicated that areas ofthe asphalt roadway that did employ the fiber composition of the presentinvention showed little or no longitudinal or transverse separationrelative to areas of the roadway that did not employ asphalt materialreinforced with the fiber compositions of the present invention. It isbelieved that embodiments of the present invention may increase the lifespan of roadways from two to three years to up to ten years in cold-mixasphalt.

The foregoing examples demonstrate that the hybrid fibers of the presentinvention when used in building material, such as cementitious material,perform as well or better than many or all prior art reinforcementfibers, including steel reinforcement fibers. Further, the foregoingexperiments demonstrate that relatively small concentrations of fiberwill support substantially improved results. These observations are bothsurprising and unexpected.

The synthetic fiber reinforced material of the present invention, andthe method by which it formed may be used to form a building materialformed of, for example cementitious material, that exhibits reducedpermeability, increased fatigue strength, improved toughness, andreduced plastic shrinkage.

Although the foregoing description has necessarily presented a limitednumber of embodiments of the invention, those of ordinary skill in therelevant art will appreciate that various changes in the configurations,compositions, details, materials, and arrangement of the elements thathave been herein described and illustrated in order to explain thenature of the invention may be made by those skilled in the art, and allsuch modifications will remain within the principle and scope of theinvention as expressed herein in the appended claims. In addition,although the foregoing detailed description has been directed to anembodiment of reinforcement fiber incorporated into cementitiousmaterial, such as concrete and asphalt, it will be understood that thepresent invention has broader applicability and, for example, may beused in connection with all building materials that may incorporatesuitable reinforcement fibers. All such additional applications of theinvention remain within the principle and scope of the invention asembodied in the appended claims.

1. A fiber reinforcement material, comprising: a plurality ofpolyolefinic strands of monofilaments of about 350 to about 6000 denierper filament, twisted to form a fiber bundle, the degree of twist beinggreater than about 0.9 turns/inch (about 0.36 turns/cm).
 2. The fiberreinforcement material of claim 1, wherein the degree of twist is lessthan about 2.2 turns/inch (about 0.87 turns/cm).
 3. The fiberreinforcement material of claim 1, wherein the degree of twist rangesfrom greater than about 0.9 turns/inch (about 0.36 turns/cm) to about1.1 turns/inch (about 0.43 turns/cm).
 4. The fiber reinforcementmaterial of claim 1, wherein the degree of twist is about 1.1 turns/inch(about 0.43 turns/cm).
 5. The fiber reinforcement material of claim 1,wherein the strands are about 750 denier per filament.
 6. The fiberreinforcement material of claim 1, wherein the strands are a copolymerformed of polypropylene and polyethylene.
 7. The fiber reinforcementmaterial of claim 6, wherein the copolymer is about 75–80 percent byweight polypropylene and about 20–25 percent by weight polyethylene. 8.The fiber reinforcement material of claim 6, wherein the polypropyleneis a low melt polypropylene and the polyethylene is a high densitypolyethylene.
 9. The fiber reinforcement material of claim 1, whereinthe length of the component is about 19 to 60mm.
 10. The fiberreinforcement material of claim 1, wherein the fiber bundle isnon-interconnected.
 11. The fiber reinforcement material of claim 1,wherein the monofilaments are nonfibrillating.
 12. A reinforcement forcementitious material, comprising: a plurality of polyolefinmonofilaments of about 350 to about 6000 denier per filament, theplurality of monofilaments being in a twisted configuration, the degreeof twist being greater than about 0.9 turns/inch (about 0.36 turns/cm).13. The fiber reinforcement material of claim 12, wherein the degree oftwist is less than about 2.2 turns/inch (about 0.87 turns/cm).
 14. Thefiber reinforcement material of claim 12, wherein the degree of twistranges from greater than about 0.9 turns/inch (about 0.36 turns/cm) toabout 1.1 turns/inch (about 0.43 turns/cm).
 15. The fiber reinforcementmaterial of claim 12, wherein the degree of twist is about 1.1turns/inch (about 0.43 turns/cm).
 16. The fiber reinforcement materialof claim 12, wherein the cementitious material is concrete.
 17. Areinforcement for cementitious material, comprising: a plurality ofpolyolefin monofilaments, the plurality of monofilaments being in atwisted configuration, the degree of twist being greater than about 0.9turns/inch (about 0.36 turns/cm), wherein the cementitious material isasphalt.
 18. A reinforced cementitious material, comprising: acementitious mass; and, a fiber component dispersed throughout the mass,the fiber component being a plurality of polyolefinic strands ofmonofilaments of about 350 to about 6000 denier per filament twisted toform a fiber bundle, the degree of twist being greater than about 0.9turns/inch (about 0.36 turns/cm).
 19. The fiber reinforcement materialof claim 18, wherein the degree of twist is less than about 2.2turns/inch (about 0.87 turns/cm).
 20. The fiber reinforcement materialof claim 18, wherein the degree of twist ranges from greater than about0.9 turns/inch (about 0.36 turns/cm) to about 1.1 turns/inch (about 0.43turns/cm).
 21. The fiber reinforcement material of claim 18, wherein thedegree of twist is about 1.1 turns/inch (about 0.43 turns/cm).
 22. Thefiber reinforcement material of claim 18, wherein the strands are acopolymer formed of polypropylene and polyethylene.
 23. The fiberreinforcement material of claim 22, wherein the copolymer is about 75–80percent by weight polypropylene and about 20–25 percent by weightpolyethylene.
 24. The fiber reinforcement material of claim 18, whereinthe length of the component is about 19 to 60 mm.
 25. The fiberreinforcement material of claim 18, wherein the monofilaments arenonfibrillating and the fiber bundle is non-interconnected.
 26. Thefiber reinforcement material of claim 18, wherein the cementitious massis concrete.
 27. A reinforced cementitious material, comprising: acementitious mass; and, a fiber component dispersed throughout the mass,the fiber component being a plurality of polyolefinic strands ofmonofilaments of about 350 to about 6000 denier per filament twisted toform a fiber bundle, the degree of twist being greater than about 0.9turns/inch (about 0.36 turns/cm), wherein the cementitious mass isasphalt.
 28. A reinforcement material for a cementitious material formedby twisting a plurality of polyolefinic strands of monofilaments ofabout 350 to about 6000 denier per filament into a fiber bundle formixing into a cementitious mass, the degree of twist being greater thanabout 0.9 turns/inch (about 0.36 turns/cm).
 29. The reinforcementmaterial of claim 28, wherein the degree of twist is less than about 2.2turns/inch (about 0.87 turns/cm).
 30. The reinforcement material ofclaim 28, wherein the degree of twist ranges from greater than about 0.9turns/inch (about 0.36 turns/cm) to about 1.1 turns/inch (about 0.43turns/cm).
 31. The reinforcement material of claim 28, wherein thedegree of twist is about 1.1 turns/inch (about 0.43 turns/cm).
 32. Thereinforcement material of claim 28, wherein the cementitious mass isconcrete.
 33. A reinforcement material for a cementitious materialformed by twisting a plurality of polyolefinic strands of monofilamentsinto a fiber bundle for mixing into a cementitious mass, the degree oftwist being greater than about 0.9 turns/inch (about 0.36 turns/cm),wherein the cementitious mass is asphalt.
 34. A reinforced cementitiousmaterial, comprising: a synthetic fiber blend distributed through amatrix of the cementitious material, the synthetic fiber blend,including: a first fiber component formed of a homopolymer polypropylenefiber; and a second fiber component being discrete from the first fibercomponent and being a copolymer formed of a polypropylene and a highdensity polyethylene, the second fiber component being a plurality ofmonofilaments twisted to form a non-interconnected bundle, the degree oftwist being greater than about 0.9 turns/inch (about 0.36 turns/cm). 35.The reinforced cementitious material of claim 34, wherein the degree oftwist is less than about 2.2 turns/inch (about 0.87 turns/cm).
 36. Thereinforced cementitious material of claim 34, wherein the degree oftwist ranges from greater than about 0.9 turns/inch (about 0.36turns/cm) to about 1.1 turns/inch (about 0.43 turns/cm).
 37. Thereinforced cementitious of claim 34, wherein the degree of twist isabout 1.1 turns/inch (about 0.43 turns/cm).
 38. The reinforcedcementitious material of claim 34, wherein the first fiber component isfibrillated and present in the synthetic fiber blend in amounts rangingfrom about 5 to about 50 by total weight percent, and the second fibercomponent is comprised of one or more twisted nonfibrillatingmonofilaments present in the synthetic fiber blend in amounts rangingfrom about 50 to about 95 by total weight percent.
 39. The reinforcedcementitious material of claim 34, wherein the first fiber component ispresent in the synthetic blend in about 6.7 total weight percent andsecond fiber component is present in the synthetic fiber blend in about93.3 percent by total weight percent.
 40. The reinforced cementitiousmaterial of claim 34, wherein the synthetic fiber blend is present inthe cementitious material in amounts ranging from about 0.1 to about 2.0percent by volume.
 41. The reinforced cementitious material of claim 34,wherein the synthetic fiber blend is present in the cementitiousmaterial in amounts ranging from about 0.5 to about 2.0 percent byvolume.
 42. The reinforced cementitious material of claim 34, whereinthe synthetic fiber blend is present in the cementitious material inamounts ranging from about 0.3 to about 2.0 percent by volume.
 43. Thereinforced cementitious material of claim 34, wherein the cementitiousmaterial is reinforced concrete.
 44. The reinforced cementitiousmaterial of claim 34, wherein the cementitious material is reinforcedasphalt.
 45. A fiber reinforcement material, comprising: a plurality ofpolyolefinic strands of monofilaments of about 350 to about 6000 denierper filament, twisted to form a fiber bundle, the degree of twist beinggreater than about 0.9 turns/inch (about 0.36 turns/cm), wherein theplurality of strands of monofilaments are twisted to form anon-interconnected bundle in the absence of a wetting agent.
 46. A fiberreinforcement material, comprising: a plurality of polyolefinic strandsof monofilaments of about 350 to about 6000 denier per filament, twistedto form a fiber bundle, the degree of twist being greater than about 0.9turns/inch (about 0.36 turns/cm), wherein the plurality of strands ofmonofilaments form a first fiber component, the fiber reinforcementmaterial further comprising a second fiber component that is discretefrom the first fiber component and is fibrillated and formed of ahomopolymer material.
 47. The fiber reinforcement material of claim 46,wherein the first fiber component is present in amounts ranging fromabout 50 to 95 weight percent and the second fiber component is presentin amounts ranging from about 5 to about 50 weight percent.
 48. Thefiber reinforcement material of claim 46, wherein the first fibercomponent and the second fiber component are blended in the absence of awetting agent.
 49. The fiber reinforcement material of claim 46, whereinthe first fiber component has a fiber length of about 19 to about 60 mmand the second fiber component has a fiber length of about 19 to about60 mm.
 50. The fiber reinforcement material of claim 46, wherein thefirst fiber component and the second fiber component have about the samefiber length.
 51. The fiber reinforcement material of claim 46, whereinthe first fiber component is a copolymer formed of a major amount of apolypropylene and a minor amount of a high density polyethylene, and thesecond fiber component is formed of a homopolymer polypropylene fiber.52. The fiber reinforcement material of claim 46, wherein the secondfiber component is about 100 to about 20,000 denier per filament.
 53. Areinforcement for cementitious material, comprising: a plurality ofpolyolefin monofilaments, the plurality of monofilaments being in atwisted configuration, the degree of twist being greater than about 0.9turns/inch (about 0.36 turns/cm), wherein the plurality of monofilamentsare twisted to form a non-interconnected bundle in the absence of awetting agent.
 54. A reinforcement for cementitious material,comprising: a plurality of polyolefin monofilaments, the plurality ofmonofilaments being in a twisted configuration, the degree of twistbeing greater than about 0.9 turns/inch (about 0.36 turns/cm), whereinthe plurality of monofilaments form a first fiber component, thereinforcement for cementitious material further comprising a secondfiber component that is discrete from the first fiber component and isfibrillated and formed of a homopolymer material.
 55. The reinforcementfor cementitious material of claim 54, wherein the first fiber componentis present in amounts ranging from about 50 to 95 weight percent and thesecond fiber component is present in amounts ranging from about 5 toabout 50 weight percent.
 56. The reinforcement for cementitious materialof claim 54 wherein the first fiber component and the second fibercomponent are blended in the absence of a wetting agent.
 57. Thereinforcement for cementitious material of claim 54, wherein the firstfiber component has a fiber length of about 19 to about 60 mm and thesecond fiber component has a fiber length of about 19 to about 60 mm.58. The reinforcement for cementitious material of claim 54, wherein thefirst fiber component and the second fiber component have about the samefiber length.
 59. The reinforcement for cementitious material of claim54, wherein the first fiber component is a copolymer formed of a majoramount of a polypropylene and a minor amount of a high densitypolyethylene, and the second fiber component is formed of a homopolymerpolypropylene fiber.
 60. The reinforcement for cementitious material ofclaim 54, wherein the first fiber component is about 350 to about 6000denier per filament and the second fiber component is about 100 to about20,000 denier per filament.
 61. The reinforcement for cementitiousmaterial of claim 54 wherein the first fiber component is formed ofabout 70 to 80 percent by weight polypropylene and about 20 to 30percent by weight high density polyethylene.
 62. A reinforcedcementitious material, comprising: a cementitious mass; and, a fibercomponent dispersed throughout the mass, the fiber component being aplurality of polyolefinic strands of monofilaments of about 350 to about6000 denier per filament twisted to form a fiber bundle, the degree oftwist being greater than about 0.9 turns/inch (about 0.36 turns/cm),wherein the plurality of strands of monofilaments are twisted to form anon-interconnected bundle in the absence of a wetting agent.
 63. Areinforced cementitious material, comprising: a cementitious mass; and,a fiber component dispersed throughout the mass, the fiber componentbeing a plurality of polyolefinic strands of monofilaments of about 350to about 6000 denier per filament twisted to form a fiber bundle, thedegree of twist being greater than about 0.9 turns/inch (about 0.36turns/cm), wherein the plurality of strands of monofilaments form afirst fiber component, the reinforced cementitious material furthercomprising a second fiber component that is discrete from the firstfiber component and is fibrillated and formed of a homopolymer material.64. The reinforced cementitious material of claim 63, wherein the firstfiber component is present in amounts ranging from about 50 to 95 weightpercent and the second fiber component is present in amounts rangingfrom about 5 to about 50 weight percent.
 65. The reinforced cementitiousmaterial of claim 63, wherein the first fiber component and the secondfiber component are blended in the absence of a wetting agent.
 66. Thereinforced cementitious material of claim 63, wherein the first fibercomponent has a fiber length of about 19 to about 60 mm and the secondfiber component has a fiber length of about 19 to about 60 mm.
 67. Thereinforced cementitious material of claim 63, wherein the first fibercomponent and the second fiber component have about the same fiberlength.
 68. The reinforced cementitious material of claim 63, whereinthe first fiber component is a copolymer formed of a major amount of apolypropylene and a minor amount of a high density polyethylene, and thesecond fiber component is formed of a homopolymer polypropylene fiber.69. The reinforced cementitious material of claim 63, wherein the secondfiber component is about 100 to about 20,000 denier per filament. 70.The reinforced cementitious material of claim 63, wherein the firstfiber component and the second fiber component form a synthetic fiberblend, the synthetic fiber blend being present in the cementitious massin amounts ranging from about 0.1 to about 2.0 percent by volume. 71.The reinforced cementitious material of claim 70, wherein the syntheticfiber blend is present in the cementitious mass in amounts ranging fromabout 0.3 to about 2.0 percent by volume.
 72. The reinforcedcementitious material of claim 70, wherein the synthetic fiber blend ispresent in the cementitious mass in amounts ranging from about 0.5 toabout 2.0 percent by volume.
 73. A reinforcement material for acementitious material formed by twisting a plurality of polyolefinicstrands of monofilaments into a fiber bundle for mixing into acementitious mass, the degree of twist being greater than about 0.9turns/inch (about 0.36 turns/cm), wherein the plurality of strands ofmonofilaments are twisted to form a non-interconnected bundle in theabsence of a wetting agent.
 74. A reinforcement material for acementitious material formed by twisting a plurality of polyolefinicstrands of monofilaments into a fiber bundle for mixing into acementitious mass, the degree of twist being greater than about 0.9turns/inch (about 0.36 turns/cm), wherein the plurality of strands ofmonofilaments form a first fiber component, the reinforcement materialfurther comprising a second fiber component that is discrete from thefirst fiber component and is fibrillated and formed of a homopolymermaterial.
 75. The reinforcement material of claim 74, wherein the firstfiber component is present in amounts ranging from about 50 to 95 weightpercent and the second fiber component is present in amounts rangingfrom about 5 to about 50 weight percent.
 76. The reinforcement materialof claim 74, wherein the first fiber component and the second fibercomponent are blended in the absence of a wetting agent.
 77. Thereinforcement material of claim 74, wherein the first fiber componenthas a fiber length of about 19 to about 60 mm and the second fibercomponent has a fiber length of about 19 to about 60 mm.
 78. Thereinforcement material of claim 74, wherein the first fiber componentand the second fiber component have about the same fiber length.
 79. Thereinforcement material of claim 74, wherein the first fiber component isa copolymer formed of a major amount of a polypropylene and a minoramount of a high density polyethylene, and the second fiber component isformed of a homopolymer polypropylene fiber.
 80. The reinforcementmaterial of claim 74, wherein the first fiber component is about 350 toabout 6000 denier per filament and the second fiber component is about100 to about 20,000 denier per filament.
 81. The reinforcement materialof claim 74 wherein the first fiber component is formed of about 70 to80 percent by weight polypropylene and about 20 to 30 percent by weighthigh density polyethylene.
 82. The reinforced cementitious material ofclaim 34, wherein the plurality of monofilaments are twisted to form thenon-interconnected bundle in the absence of a wetting agent.
 83. Thereinforced cementitious material of claim 34, wherein the first fibercomponent and the second fiber component are blended in the absence of awetting agent.
 84. The reinforced cementitious material of claim 34,wherein the first fiber component is about 100 to about 20,000 denierper filament, and the second fiber component is about 350 to about 6000denier per filament.
 85. A fiber reinforcement material, comprising: aplurality of polyolefinic strands of monofilaments of about 350 to about6000 denier per filament, twisted to form a fiber bundle in the absenceof a wetting agent.
 86. The fiber reinforcement material of claim 85,wherein the reinforcement is a reinforcement for cementitious material.87. The fiber reinforcement material of claim 86, wherein thecementitious material is concrete.
 88. The fiber reinforcement materialof claim 86, wherein the cementitious material is asphalt.
 89. Areinforcement for cementitious material, comprising: a plurality ofpolyolefin monofilaments of about 350 to about 6000 denier per filament,the plurality of monofilaments being in a twisted configuration in theabsence of a wetting agent.
 90. The reinforcement of claim 89, whereinthe cementitious material is concrete.
 91. The reinforcement of claim89, wherein the cementitious material is asphalt.
 92. A reinforcedcementitious material, comprising: a cementitious mass; and, a fibercomponent dispersed throughout the mass, the fiber component being aplurality of polyolefinic strands of monofilaments of about 350 to about6000 denier per filament twisted to form a fiber bundle in the absenceof a wetting agent.
 93. The reinforced cementitious material of claim92, wherein the cementitious material is concrete.
 94. The reinforcedcementitious material of claim 92, wherein the cementitious material isasphalt.
 95. A reinforcement material for a cementitious material formedby twisting a plurality of polyolefinic strands of monofilaments ofabout 350 to about 6000 denier per filament into a fiber bundle in theabsence of a wetting agent for mixing into a cementitious mass.
 96. Thereinforcement material of claim 95, wherein the cementitious material isconcrete.
 97. The reinforcement material of claim 95, wherein thecementitious material is asphalt.
 98. A reinforced cementitiousmaterial, comprising: a synthetic fiber blend distributed through amatrix of the cementitious material, the synthetic fiber blend,including: a first fiber component formed of a homopolymer polypropylenefiber; and a second fiber component being discrete from the first fibercomponent and being a copolymer formed of a polypropylene and a highdensity polyethylene, the second fiber component being a plurality ofmonofilaments of about 350 to about 6000 denier per filament twisted toform a fiber bundle in the absence of a wetting agent.
 99. Thereinforced cementitious material of claim 98, wherein the cementitiousmaterial is concrete.
 100. The reinforced cementitious material of claim98, wherein the cementitious material is asphalt.